Four United Nations workers kidnapped by rebels in southern Sudan a week ago have been released.

A UN spokeswoman said the men were exhausted but well, and were being examined by doctors.

They were freed in Fanjak, about 470 miles (750km) south of the capital, Khartoum, where they had been held captive since pro-government militia hijacked their aircraft last Thursday.

Three of them - an American working for Unicef and two Kenyan pilots - were flown to northern Kenya's Lokichokio base, headquarters of the UN-sponsored humanitarian Operation Lifeline Sudan (OLS).

The fourth detainee, a Sudan national employed by Unicef, was taken to Malakal, capital of south Sudan's Upper Nile State.

Insecurity

According to the UN, the aircraft remains in Fanjak with mechanical problems.

The militia had alleged that a UN plane had flown three of its commanders to another location last month where they were arrested by rivals.

The insecurity in the region prompted the UN to suspend aid to an estimated 280,000 displaced people.

An OLS spokesman said the releases did not mean that aid would resume, and added that inquiries would be made in Khartoum as to the whereabouts of the Sudanese official who did not return to Kenya.