Three oil workers who were held hostage by Libyan militants were brought to Malta after their release on Friday.

The workers - two from Bangladesh and one from Ghana - are employees of Malta-based Value Added Oilfield Services (VAOS).

Another six hostages are still unaccounted for. They were seized two weeks ago in a raid in which 11 people were killed. 

The Maltese government said two of the released hostages have already left for their own countries and the other will leave shortly.

"All three are in good health and have reported that they were treated well during their captivity," VAOS said, hailing the "fantastic news" of their release but reiterating its commitment to get the six others out as well. They include four Filipinos, a Czech, and an Austrian.

"The three workers now released have been separated from their other six colleagues on the second day of their captivity and hence could not provide any further information as to the whereabouts and the well-being of their colleagues," VAOS said, but expressed hope the information they provided may help secure the others' release.

Foreigners have increasingly become targets in Libya's turmoil, where two rival governments are battling for control and Islamist extremists are proliferating in the chaos that followed Muammar Gaddafi's ouster four years ago.

Western governments are backing U.N. negotiations to end the crisis in Libya, worried that the large North African state just across the Mediterranean from mainland Europe is becoming a haven for Islamist militants.

Libyan militants claiming loyalty to Islamic State in Iraq and Syria have been blamed for high-profile attacks this year involving foreigners, including an assault on a Tripoli hotel and the beheading of a group of Egyptian Christians.