300 militants reported killed in joint ground offensive – featuring soldiers from Chad and Niger – raising hopes tide is turning against extremists.

The thousands of foreign troops pouring into northern Nigeria to join the fight against Boko Haram have seized two towns from the Islamist extremists after fierce battles, accordingt to military sources.

Forces from neighbouring Chad and Niger killed about 300 militants as they gained control of Malam Fatouri and Damasak on Monday, a military source from Niger told Reuters. About 10 Chadian soldiers were killed and 30 Nigerien and Chadian soldiers were injured.

The joint ground and air offensive raised hopes that the tide is turning against the extremist group, which last week pledged allegiance to Islamic State, and that elections postponed to 28 March will go ahead as planned.

Boko Haram had held Damasak, six miles (10km) south of the Niger border, since November. “We have kicked the enemy out of these areas and they are now under our control,” the Nigerien source told Reuters. “We had permission from Nigeria for this action.”

Witnesses in the town of Bosso in Niger reported a convoy of about 200 military vehicles crossing over into Nigeria since Saturday, according to the Associated Press. Adam Boukarna, a resident, said the deployment was followed by loud explosions, indicating heavy combat.

Edgard Alain Mebe Ngo’o, Cameroon’s defence minister, said troops from Nigeria and Chad would fight Boko Haram while soldiers from Cameroon and Niger would guard their borders to prevent the militants from escaping. Boko Haram has been using Cameroon as an escape and supply route.

The move follows years of faltering attempts to overcome political differences and combine regional strengths against the insurgency. The US, Britain, France and the European Union are backing the creation of a multinational force of 8,750 troops led by Nigeria and Chad with contingents from Cameroon, Niger and Benin. Several other countries also have pledged to help.

Dr John-Mark Iyi, a Nigerian political analyst based at the University of Johannesburg in South Africa, said: “This cooperation is something long overdue and should mark the beginning of a turn of events. It is the lack of this cooperation that has contributed to the ineffectiveness of anti-insurgency tactics that Nigeria was adopting.

“In the past Nigeria has had a frosty relationship with its francophone neighbours and has found it easier to collaborate with Ghana, an anglophone country. There have been accusations and counter-accusations: who is leaking intelligence, who is a fifth columnist.”

But Nigeria’s neighbours were forced to act after Boko Haram crossed into their territories, carrying out attacks and kidnappings, Iyi added. “It becomes very apparent in the circumstances that it is in their interests to cooperate against a common enemy for the sake of stability in the region. The African Union was belated in responding but realised it was not only a Nigerian problem but a regional problem.”

Nigeria’s military has been dogged by low pay, low morale and lack of equipment. Niger’s army has only 5,200 troops, one of the smallest in the world, while Cameroon’s stands at just 12,500 soldiers. Chad’s military is more formidable, with 20,000 soldiers battle-hardened by previous experience of combating insurgents. However, there are fears that even if Boko Haram loses territory, it could resort to its old hit-and-run tactics of gun attacks and bombings in major towns.

The group has been fighting a near six-year insurgency against the Nigerian government that has recently included using women and girls as suicide bombers. It has also carried out mass kidnappings, most infamously of 276 schoolgirls in Chibok last year.

On Saturday, the Boko Haram leader, Abubakar Shekau, pledged his group’s allegiance to Islamic State, which rules a self-declared caliphate in parts of Iraq and Syria, raising fears that the conflict largely restricted to north-east Nigeria could suck in Isis fighters from north Africa.

Earlier that day, Boko Haram was blamed for four suicide bomb attacks that police said killed at least 54 people and wounded 143 in the north-east city of Maiduguri, the capital of Borno state and birthplace of the group, whose name means “Western education is forbidden” in the Hausa language.

Nigeria postponed national elections by six weeks until 28 March to gain more time to try to improve security in the north. Antony Goldman, a Nigeria analyst and head of London-based PM Consulting, said: “When they postponed the elections citing security, a lot of people were sceptical. The opposition said it was a device to help the ruling party. The ruling party said it was device that would allow the election commission to save face.

“It turns out, in a very Nigerian way, it was all true. Many more voting cards have been handed out and something has changed on the battlefield. Chadian troops have done a very good job of securing the border and going into Nigeria. That’s also freed up Nigerian troops at a time they’re also making some headway with procurement of helicopters, armoured personnel carriers and thermal imaging equipment that allows them to attack camps at night.”

The Nigerian president, Goodluck Jonathan, has been criticised for failing to defeat the insurgency and accused of delaying the election, originally set for 14 February, because he faces defeat.

Goldman added: “All of these gains have come after the election should have been won and lost. It will be bound to have an effect on the election when it happens. This issue was the opposition’s strongest suit.”