Nigeria has brought in hundreds of foreign mercenaries in recent weeks from South Africa and other countries in a bid to boost its fight against Boko Haram, according to security forces and diplomatic sources.

The reported presence of foreign fighters, equipped with heavy weaponry, attack helicopters and armoured vehicles, adds to the already broad array of forces, including soldiers from Chad, Niger, Cameroon and Benin in the conflict against Boko Haram.

The reported use of mercenaries comes as Nigeria prepares to hold general elections on March 28, which was delayed by six weeks in order to buy time to recapture territory and restore stability in the country’s conflict-ridden northeast.

Nigerian officials have so far refused to comment on the reports of mercenaries.

In an interview with Voice of America late on Wednesday, Nigerian President Goodluck Jonathan said two companies were providing “trainers and technicians” to help Nigerian forces, without providing more details.

‘Private military firm link’

But a West African security source and a South African defence source said the foreign troops were linked to the bosses of former South African private military firm Executive Outcomes, according to the Reuters news agency.

Executive Outcomes was best-known for its involvement in Angola’s 1975-2002 civil war and against Revolutionary United Front rebels in an internal conflict in Sierra Leone in 1995.

The West African security source said several hundred foreigners were involved in running major offensive operations against Boko Haram, and were being paid around $400 a day in cash.

Their impact on the fighting so far could not be quantified, but the general run of the campaign has seen the tide turn somewhat against Boko Haram in recent weeks.

‘Desperate ploy’

Separately, a South African defence contractor confirmed to Reuters that ex-Executive Outcomes leaders were involved in the deployment.

“It’s an incoherent mix of people, helicopters and random kit from all sorts of different sources, but there is an element of internal cohesion from the Nigerian army,” the diplomat said.

“It appears to be a desperate ploy to get some sort of tactical success up there in six weeks for the electoral boost,” the diplomat added. The numbers of soldiers involved were in the “low hundreds”, the diplomat added.

After reports of South African military trainers first surfaced in the Afrikaans-language Beeld newspaper in January, Defence MinisterNosiviwe Mapise-Nqakula made clear her displeasure, saying any deployment would be illegal under 1998 anti-mercenary laws.

“They are mercenaries, whether they are training, skilling the Nigerian defence force, or scouting for them. The point is they have no business to be there,” she was quoted as saying in domestic media this month. Al Jazeera