Recent weeks have seen demonstrators, for the most part students, take to the streets of Khartoum - and to a lesser extent other Sudanese cities - to protest against the rising cost of living and call for an end to the 23-year rule of President Omar al-Bashir.
Meanwhile, armed rebellions have been active in the western region of Darfur for almost a decade and broke out in the southern border state of South Kordofan in June 2011 and later in nearby Blue Nile State.
Sudan is in the throes of an economic crisis sparked by the July 2011 secession of South Sudan, which, when it was part of Sudan, produced three-quarters of the oil that almost solely drove the country's economy. In June 2012, inflation was running at 37 percent. The government is faced with a budget deficit of US$2.4 billion.
While backed by the International Monetary Fund, Khartoum's austerity measures, such as cutting fuel subsidies and government jobs, devaluing the currency and raising taxes have sparked a series of modest yet growing protests (with their own Twitter hashtag, #sudanrevolts), which in turn have prompted a robust response from security services.
Bashir has derided the demonstrators as "elbow-lickers", an allusion to the supposed futility of their protests.
"They talk of an Arab Spring - let me tell them that in Sudan we have a hot summer, a burning hot summer that burns its enemies," the president declared in mid-July.
Here is a brief overview of anti-government forces which, despite some alliances, lack strong cohesion or coordination among their various elements:
URBAN PROTEST MOVEMENTS
Girifna Movement (GM) A popular resistance movement formed in October 2009 by university students, GM works for peaceful change in Sudan. Girifna means "we are fed up".
GM asks questions like: "Aren't you fed up with the monopoly over political power by them?" "Aren't you fed up with the high cost of living?" "Aren't you fed up with the electricity and water shortages?" "Aren't you fed up with what's happening in Darfur?" Girifna uses street demonstrations, Radio Girifna, an online magazine, public speeches and newsletters, etc. to get its message across.
Girifna says its members have been beaten, abducted, and imprisoned by state security forces.
Sudan Change Now (SCN) SCN was established in 2010 by young activists working for peaceful democratic change. It is a youth movement which gets its message across using internet-based social media.
SCN's Facebook page says: "We believe that the current regime in Sudan is completely dysfunctional and it is our collective responsibility as Sudanese to put an end to it. Change is our way towards the better future that our nation deserves."
"We are working on creating a common front of solidarity that brings together all those who are suffering from the actions of the current corrupt and evil regime. Together we work to ensure a unified and effective course of action to overthrow the regime and build a new brighter future for our coming generations."
Sudan Revolutionary Front (SRF) alliance Led by SPLM-N (see below) chairman Malik Aggar, SRF is a coalition of rebel groups in Darfur, South Kordofan, Blue Nile and eastern Sudan formed in November 2011. SRF leaders say they want to overthrow the NCP regime "using all available means" and establish a secular, liberal state.
In a press statement on 12 July 2012 SRF said it supported the urban protests against the government. It said support by the National Consensus Forces (see below) for the Sudanese people's "revolt" was a step in the right direction. It called on all political opposition forces to hold an expanded meeting on how to create a joint work programme, agree on a national democratic programme, and work together to bring down the regime.
SRF includes SPMN-N, JEM, SLA-AW, SLA-MM and the Beja Congress.
Sudan People's Liberation Movement - Northern Sector (SPLM-N) This was initially the northern wing of the politico-military group which led the southern rebellion during the 1983-2005 civil war and which is now in power in the newly independent state of South Sudan.
Khartoum has frequently dismissed the SPLM-N's insistence that it has operated as an independent entity since secession in July 2011, saying that its armed rebellion in Blue Nile and South Kordofan is controlled from Juba.
Regime change is a key policy tenet of the SPLM-N, whose political activities the government has banned since late 2011.
Justice and Equality Movement (JEM) JEM is a rebel group involved in the Darfur conflict founded by Khalil Ibrahim, who was killed by the Sudanese Armed Forces in December 2011. Currently JEM is led by Khalil's brother, Jibril Ibrahim, whose succession has agitated simmering fault lines, largely along ethnic lines involving non-Zaghawa, Missiriya Arabs, and some Zaghawa previously aligned with the Sudan Liberation Army - Minni Minnawi faction (SLA-MM).
The diaspora-based Democratic JEM (DJEM) is a splinter group launched by predominantly non-Zaghawa dissidents in April 2006, in rejection of JEM's domination by the Kobe, a Zaghawa sub-group. JEM was established in early 2003 by a group of educated, politically experienced Darfuris, and drew most of its initial leadership and members from the Kobe, who are more numerous in Chad than in Darfur.
While JEM is considered the strongest armed rebel group in western Sudan it continues to lack a wider constituency among Darfuris.
The JEM Corrective Leadership (JEM CL) under Zakaria Musa, is a new breakaway movement that emerged in mid-January 2012 following Khalil Ibrahim's death.
Sudan Liberation Army-Abdul Wahid faction (SLA-AW) SLA-AW is a Darfur rebel group emerged from the split of the Sudan Liberation Army into numerous factions.
The original SLA was formed in 2001 as an alliance between Fur and Zaghawa ethnic groups with differing goals: the Fur envisaged their rebellion as being essentially anti-government, in favour of a new, decentralized Sudan, while the Zaghawa's focused more on Arab militias with whom they were in economic competition in North Darfur.
Abdul Wahid Mohammed al-Nur, SLA's original chairman, has spent most of the period since the Darfur rebellion started in 2003 outside the region, first in Paris and more recently in Uganda. This absence has led to dissent and divisions within his movement.
SLA-AW, the Fur-led faction, has not signed the 2006 Darfur Peace Agreement and has not taken part in any peace talks.
Sudan Liberation Army - Minni Minnawi faction (SLA-MM) A former teacher with little prior military experience, Minawi led SLA's main forces before the group split. In 2006 he signed the Darfur Peace Agreement (DPA) with Khartoum and gained the largely nominal positions of - until April 2010 - senior assistant to Bashir, and chairman of the Transitional Darfur Regional Authority.
In late 2010 Minawi moved to Juba, capital of what is now South Sudan, and disowned the DPA, leading the Sudanese army to declare his faction a legitimate target. This unleashed a new wave of violence in SLA-MM areas. Minawi's move also divided the faction into: a group which continued discussions with Khartoum, another in North Darfur negotiating with JEM and a third which remained loyal to Minawi himself.
The formation of the SRF led to some rapprochement between the two SLA factions.
Several Sudanese opposition parties are grouped under the banner of the National Consensus Forces, originally formed to stand against the ruling National Congress Party in elections held in April 2010.
Some of these - the National Umma Party, the Communist Party and the Popular Congress Party - signed a Democratic Alternative Charter (DAC) on 4 July 2012, thereby committing themselves to remove the NCP from power through "peaceful means" and the creation of a "civil democratic state".
The NCF includes:
The National Umma Party (NUP):
President: Al Saddig Al-Mahdi
Secretary-General: Ibrahim al-Amin
Prominent member: Mariam al-Sadiq al-Mahdi
NUP's origins go back to the 19th century. Its current president was the prime minister of Sudan on two occasions (1966-67), and (1986-89).
Popular Congress Party (PCP):
President: Hassan Al-Turabi
PCP split from the ruling National Congress Party in 2000. It describes itself as "a broad national democratic party" not based upon regionalism or sectarianism. PCP publishes its own newspaper, Rai al-Shaab, currently banned by the National Intelligence Security Services.
PCP website: www.popularcongress.org
Sudanese Communist Party (SCP):
Secretary-general: Mohamed Mukhtar Al-Khateeb
SCP is one of the oldest parties in Sudan. It advocates socialism in a multi-party system.
SCP website: www.midan.net
Other DAC signatories:
Nasirist Democratic Unionist Party (NDUP): supports Arab nationalism; has a close affinity with Egypt; led by Gamal Abdunnasir Idris.
The Unified Democratic Unionist Party - led by Jala'a Ismail Al-azhari
New Forces Democratic Movement (HAG) - led by Halal Abdulhaleem
Sudan Ba'ath Party - led by Mohamed Ali Jadain
The Arabic Baath Social Party - Originally led by Ali Elraih El Sanhoory
Sudanese Congress Party - led by Ibrahim Elshiekh