Armed bandits shot dead three people and wounded eleven in a series of attacks on buses driving along the main trans-Sahara highway in northern Niger earlier this week, the Niger government said.
The attackers also kidnapped two policemen in the incidents, which took place on a remote stretch of desert road on Tuesday, it added.
Interior Minister Albade Abouba said in a statement read on national radio television on Wednesday night that all three ambushes occurred on the road between Agadez, the main town in northern Niger, and Arlit, a uranium mining settlement 240 km to the north.
The attackers, who were travelling aboard two four-wheel drive vehicles, fired indiscriminately at the buses, killing three passengers, including a two-year-old child, he said.
The hail of gunfire also wounded a further 11 passengers, he added.
The Interior Minister said the bandits robbed the travellers of their possessions and then drove off, taking with them two policemen who had been travelling as passengers on one of the buses.
This was the most serious incident to take place in northern Niger since a group of armed men machine-gunned a bus near Agadez on 5 June, injuring two people. In a separate incident the same night, gunmen robbed a truck on the other side of the town.
Some people believe the gunmen to be supporters of Rhissa Ag Boula, a former Tuareg rebel leader. He was sacked as a government minister in February and was arrested shortly afterwards in connection with the murder of an official of Niger's ruling party in Agadez, 800 km northeast of the capital Niamey.
However, the Interior Minister insisted on calling the gunmen bandits not rebels. He said the government was taking all possible measures to identify and neutralise them.
An employee of the national bus company SNTV said one of his company's vehicles had been hit in the latest ambush.
"One of our air conditioned 52 seater buses was attacked on Tuesday around 8 p.m. 50 km from Arlit," he told IRIN by telephone from Arlit.
A four-year rebellion by Tuareg nomads in northern Niger came to an end with a peace agreement in 1995. As part of the peace settlement, many rebel fighters were integrated into the army and several of their leaders, including Ag Boula, were given senior positions in government.
The arrest of Ag Boula earlier this year was followed by reports that a large group of former Tuareg rebels had deserted from the army and raised fears that a new rebellion was afoot. However the government denied the reported desertions, saying that just five men had gone absent without leave.
The deteriorating security situation in northern Niger prompted the United Nations to impose tighter travel restrictions on UN employees in the area last June.