The spate of attacks came as the UN Security Council was preparing to discuss possible sanctions against Khartoum over the conflict in Darfur which has caused a major humanitarian crisis.

Officials said the 22 workers involved in a vaccination progr-amme were seized by the Justice and Equality Movement in an area near the South Darfur state capital of Nyala, although there was no independent confirmation.

Another group of eight Sudanese nationals working for the Red Crescent and the UN's World Food Programme were kidnapped over the weekend in Darfur.

A WFP spokeswoman said the abduction occurred 80 kilometres (50 miles) south of the North Darfur state capital of El Fasher as the group was registering some of the more than 1.2 million people displaced by a bloody government crackdown on ethnic minority rebels.

The government also blamed that kidnapping on rebels that have been battling the army and allied militias for the past 18 months, although a spokesman for the Justice and Equality Movement denied any involvement.

The Security Council is expected Thursday to hear a report on the situation in Darfur, where more than 30,000 people have been killed and an estimated 1.4 million people have fled their homes.

The council had set an August 30 deadline for Sudan to rein in pro-government militias accused of conducting an ethnic cleansing campaign in Darfur and to ease restrictions on humanitarian aid in the region or face possible sanctions.