Bomb blasts kill dozens at Nigeria military checkpoint

At least three bomb explosions killed 36 people at a military checkpoint in the northeastern Nigerian town of Biu on Tuesday, witnesses and a hospital source said.

It was not immediately clear who was behind the blasts. Biu has been repeatedly been attacked by Boko Haram, and the use of multiple bombs planned to go off in quick succession is a trademark tactic of the armed group. 

The military fired back on the attackers, killing 17 of them, a security source told Reuters. There were children around the checkpoint when the blasts occurred, said witness Auwalu Ibrahim, a local pro-government vigilante.

A care worker at Biu general hospital told Agence France-Presse that the deathtoll from the blasts had climbed to 36. Six people were receiving treatment for wounds, she said. The military did not respond to a request for comment, Reuters reported. 

Meanwhile, explosions and a burst of gunfire killing one police police officer and wounding several people and sent crowds running at a campaign rally in southern Nigeria's Rivers state on Tuesday, in another incident of unrest before elections set to take place next month. A reporter covering the rally was also stabbed, AFP reported. 

The Rivers state violence erupted at the opposition All Progressives Congress' (APC) meeting of governorship candidate Dakuku Peterside in Okrika, the hometown of President Goodluck Jonathan's wife Patience. Jonathan is a member of the ruling People’s Democratic Party (PDP). 

Rivers state has previously been struck with several bomb blasts — none of which killed civilians — in the buildup to elections, which were set for Feb. 14 but postponed until March 28 over security concerns over Boko Haram. 

Political tension has raged in Rivers state since outgoing Gov. Rotimi Amaechi defected to the APC from the PDP in 2013. Amaechi, who was not at the rally, blamed his former party for the incident. 

"It is intimidation. They don't want people to come out and vote because they know they'll lose," he said.

However, PDP spokesman for Rivers state Emmanuel Okah said it was a clash between rival “cultists,” referring to Nigerian university gangs who combine occult rituals with criminal activities. 

Police were not immediately available to comment on the identities of the gunmen involved in Tuesday's attack, AFP reported. 

Nigeria’s National Human Rights Commission last week said 58 people had been killed in political violence in the run up to polls. 

The commission pointed to oil-producing Rivers, which is seen as a key swing state in the Niger Delta, as a flashpoint area for potential unrest. 

In the national campaign, Jonathan faces a tough test against the APC's Muhammadu Buhari, a former military ruler.

Jonathan comes from neighboring Bayelsa and had previously banked on massive support across the Niger Delta, but Amaechi's defection to the APC has changed the political dynamics. Losing Rivers state could ruin Jonathan's re-election hopes.

Meanwhile, suspected Boko Haram fighters have attacked a Cameroonian military base near the border with Nigeria, killing at least five soldiers, an army colonel said Tuesday.

Col. Joseph Nouma told The Associated Press that hundreds of Boko Haram fighters escaped back to Nigeria on Monday after looting scores of homes in the area and setting fire to them. Eight wounded Cameroonian soldiers were brought to a military hospital in the capital, he said.

The renewed cross-border violence came as heads of states from Central African countries were ending a meeting in the Cameroonian capital, Yaounde, to plan the creation of a joint military response to the growing regional threat posed by Boko Haram.

The 10 member states announced that they had contributed more than 50 percent of the $100 million needed to fight the armed group. They also called on Nigeria to cooperate by allowing the multinational joint task force to attack Boko Haram in its strongholds in Nigeria.

The Nigeria-based armed group has fought a five-year insurgency against the government there, and recently began stepping up its attacks against neighboring countries after Cameroon, Niger, Chad and Benin agreed to contribute troops toward a regional military effort.

The violence has forced about 157,000 people to seek refuge in Niger, while 40,000 others have gone to Cameroon and 17,000 are in Chad, the U.N. said. Almost 1 million Nigerians are internally displaced, according to the country's own statistics. 

Al Jazeera and wire services