Four Filipinos, an Austrian and four other foreigners were abducted in an attack on a Libyan oilfield last week, official sources said Monday, after an assault blamed on Islamic State jihadists.

Eight guards were killed in the surprise attack on the southern oilfield of Al-Ghani on Friday, the Libyan unit tasked with protecting oil installations has said.

The Libyan National Oil Company also said at the time that two foreigners — an Austrian and a Filipino who worked for a services company — were missing after the attack.

Austria's foreign ministry, which had confirmed that one of its nationals was missing, said Monday that there were "reliable information" that they were "in the hands of ISIS terrorists".

The ministry said in a statement that there were "no signs to indicate whether they are dead or alive".

The missing Austrian, who is 39 years old, was named in unconfirmed Austrian media reports as Dalibor S., a father-of-two oil manager and former soldier from the northern city of Linz.

Philippines foreign department spokesman Charles Jose said Manila's embassy in Tripoli had reported that four Filipinos and five foreigners had been snatched, including the Austrian, two Bangladeshis, a Czech national and a Ghanian.

The attack "underscore[s] the escalating threat to the safety and security of Filipino oil workers in Libyan oil fields which have been targeted by armed groups in recent weeks," Jose told a news conference, adding that no demands had been issued.

A total of seven Filipinos have now been abducted in the North African state this year and the fate of another three seized in the Al-Mabruk oilfield early last month remains unknown.

Libya has been wracked by conflict for the past four years, with rival governments and powerful militias battling for control of key cities and the country's oil riches.

There were 13,000 Filipinos working in Libya when the Philippine government ordered mandatory repatriation in July 2014, the foreign department said.

The government and private employers have since brought many home, but about 4,000 others have remained, lured by salaries they could not expect in the Philippines.

Some one in 10 Filipinos work overseas.

"In view of this worsening situation we appeal once again to the estimated 4,000 plus Filipinos who are still in Libya to get in touch with our embassy in Tripoli," Jose said.

VAOS Oil Services, an Austrian contractor for the Al-Ghani oilfield, had evacuated dozens of other Filipino workers to the Libyan capital before the attack, Jose said, adding that many will now return to the Philippines.