China on Monday expressed worry over the fate of two of its nationals abducted along with others from an oilfield in the war-torn Kordofan region.

An official at Beijing's Khartoum embassy said "there are two" Chinese missing, updating earlier information from Sudan's military which said one Chinese was among those kidnapped on Friday.

Algeria's foreign ministry on Sunday confirmed that one of its citizens was also kidnapped "during an attack by an armed group on an oilfield in the province of West Kordofan where our national works for a Sudanese company".

A second Algerian was wounded and taken to hospital.

"We are very concerned about the safety of the Chinese people. So we keep contact with the Sudanese government and hope they can save them as soon as possible," the Chinese embassy official told AFP, asking for anonymity.

Sudan's army spokesman earlier reported that a Chinese, an Algerian and a Sudanese had been abducted but sources familiar with the incident told AFP on Monday that four or five Sudanese were taken along with the three foreigners.

One source said the incident occurred in Heglig district, with El Muglad the nearest major town.

Anti-government rebels have periodically claimed attacks in the Muglad area but the source familiar with the incident said various armed groups -- from militias to armed tribes and rebel splinter factions -- operate in the region.

Many might have an interest in attacking oil workers, in search of money, the source said.

Just over the border from Muglad in neighbouring Darfur, international peacekeepers have reported an alarming escalation of violence by various armed groups including criminals.