Nigerian forces have killed more than 300 Boko Haram fighters during an operation to recapture 11 towns and villages since the start of the week, the military said on Wednesday, as its war increasingly sucked in neighbours Cameroon, Chad and Niger.

The latest fighting comes as the tide has appeared to turn against Boko Haram, with neighbouring countries plagued by cross border attacks weighing in against the insurgents.

Amid growing global concern, Nigeria, Chad, Cameroon, Niger and Benin are preparing a 8 700-strong force to fight the Islamists.

“Weapons and equipment were also captured and some destroyed,” Nigerian defence spokesman Major-General Chris Olukolade said of the latest fighting. “However, two soldiers lost their lives while 10 others were wounded.”

It was not possible to independently verify the military's statement. Nigerian forces have in past been accused of overstating enemy casualties while greatly understating their own and those of civilians caught in the crossfire.

Cameroonian forces supported by Chad's air force carried out air strikes and used heavy artillery against Boko Haram in the village of Gourgouroon, on the Nigeria-Cameroon border, Cameroon army spokesman Colonel Didier Badjeck said.

In relentless attacks on military and civilians, Boko Haram have killed thousands and abducted hundreds since the group launched its violent campaign for a breakaway Islamic state in mid-2009, threatening the stability of Africa's biggest economy and top oil producer as well as that of the entire region.

Boko Haram was cited as a reason for postponing by six weeks a Nigerian presidential election that had been due to take place this past Saturday. On Tuesday, Boko Haram leader Abubakar Shekau appeared in a video monitored by the US-based SITE Intelligence Group in which he threatened to disrupt the upcoming vote. The militants see democracy as un-Islamic.

Nigerian soldiers said they had recaptured the strategic town of Monguno, on the shores of Lake Chad where the four countries meet, from Boko Haram on Monday. More than 5 000 people fled the town after the insurgents seized it last month.

Olukolade said troops had seized five types of armoured fighting vehicles, an anti-aircraft gun, 50 cases of bombs, eight different types of machine guns, some 50 cases of ammunition and 300 motorcycles the rebels use to launch attacks.

Chadian troops cleared Boko Haram out of the Nigerian town of Gamburu earlier this month. Niger soldiers shot dead a suicide bomber suspected of belonging to Boko Haram on Monday after he tried to detonate an explosive belt near a military post in the town of Bagara in southern Niger.

At least 36 civilians were killed when an unidentified airplane bombed a border village in Niger, the Niamey government said on Wednesday.

A local official in the village of Abadam blamed the Nigerian air force for the incident. Military officials in Niger said the air crew was likely to have mistaken the villagers, who had gathered for a funeral near a mosque, for Boko Haram militants.

A Nigerian military spokesman did not respond to a request for comment. Violence in the northeast has hurt the re-election prospects of President Goodluck Jonathan, accused of doing too little to protect civilians from the militants, although recent victories could swing public opinion in his favour.

The growing co-operation between Nigeria's neighbours is also attracting donor support to fight the Islamists, with the U.S. army providing equipment and intelligence to allies.

Presidents from the 10-nation Economic Community of Central African States (CEEAC) pledged on Monday to create an emergency fund of 50 billion CFA francs ($87 million) for the fight.