Nigeria: Three Foreign Doctors Killed At Home

Three North Korean doctors have been killed, one of them beheaded, in northeastern Nigeria.

A gang armed with machetes is believed to have carried out the attack on the men at their flat in Potiskum, a town in Yobe state.

Sunday's attack comes just days after gunmen on motorbikes shot dead nine women administering polio vaccinations in Kano, a major northern city.

The victims of the latest attack had no security guards at their residence and travelled around the city via three-wheel taxis without a police escort, officials said.

The Koreans, whose bodies were found by neighbours, had been working in the city since 2005.

Police arrived at the scene to find two of the victims had their throats slit, the third beheaded, and all bearing what appeared to be machete wounds. Their wives had been spared.

No one has claimed responsibility for the attack, though it is thought a radical Islamic sect known as Boko Haram may be behind the killings.

The attacks have raised questions over whether the sect, targeted by Nigeria's police and military, has picked a new soft target in its guerrilla campaign of shootings and bombings across the nation.

There are also fears that the sect may have splintered into smaller, independently operating terror groups.

In a statement, Nigerian President Goodluck condemned the killings of the polio workers as "dastardly terrorist attacks" and vowed to track down the perpetrators.

He also pledged that efforts to cut child mortality would not be stopped by "mindless acts of terrorism".

Four Chinese construction workers were shot dead by gunmen in two separate attacks in October and November last year in Borno state, which neighbours Yobe.

In December, militants in Pakistan killed at least nine workers on a polio vaccine campaign. There, the Taliban has accused health workers of acting as US spies and claimed the vaccine makes children sterile or impotent.