Multiple blast hits northeast Nigerian town of Biu

MAIDUGURI, Nigeria (Reuters) - At least three explosions struck a military checkpoint in the northeast Nigerian town of Biu on Tuesday, witnesses and a security source said. Witness Auwalu Ibrahim, a local pro-government vigilante, said there were children around the checkpoint when the blasts went off. "Everyone has been told to go home due to apprehension about the blasts," he said. Biu has been repeatedly attacked by the Islamist militant group Boko Haram and the use of multiple bombs planned to go off in quick succession is a trademark tactic of the jihadists. Boko Haram's relentless attacks on military and civilians have killed thousands since the group launched its violent campaign for a breakaway Islamic state in mid-2009. It has become the main threat to the stability of Africa's biggest economy and leading oil producer, as well as a major threat to the surrounding region. Neighbours Niger, Chad and Cameroon are all engaged in fighting the rebels. Tens of thousands of people marched through Niger's capital Niamey on Tuesday to support their military following a series of Boko Haram attacks along the Nigeria border. Nigerian soldiers recaptured two towns on Monday as U.S. and regional troops began war games in neighbouring Chad in a growing international campaign. Involvement by Nigeria's neighbours, especially battle-hardened Chadians, has tipped the balance against Boko Haram, whom the Nigerian military had been struggling to contain. Boko Haram was cited as a reason for postponing by six weeks the election that was due to take place on Saturday.