Two Serbian embassy staff members abducted in Libya in November are believed to have been among nearly 50 people killed on Friday in U.S. air strikes on a suspected Islamic State training camp, Serbia's foreign minister said.

U.S. officials said the site targeted in the strikes was a camp used by up to 60 militants including Tunisian Noureddine Chouchane, blamed for two attacks on tourists in Tunisia last year that left dozens dead.

Sladjana Stankovic, a Serbian communications officer, and Jovica Stepic, a driver, were taken hostage on Nov. 8 after their diplomatic convoy, including the ambassador, came under fire near the coastal city of Sabratha.

"We are expecting identification of the victims, so formally we cannot confirm the information," Foreign Minister Ivica Dacic told a news conference on Saturday.

The mayor of Sabratha, Hussein al-Thwadi, said Libyan authorities had sent photos of the bodies to Serbian diplomats for an initial identification.

He said the death toll from Friday's strikes had risen to 49.

It was the second U.S. air raid in three months against Islamic State in Libya, where the militants have exploited chaos following Muammar Gaddafi's 2011 downfall to build up a presence on the southern shores of the Mediterranean Sea.

On Saturday, Libya's attorney general said one of six wounded survivors told prosecutors that those in the building that was hit were "members of Islamic State who came to Libya recently for training and then to carry out terrorist acts in Tunisia".

But the Sabratha mayor said the building was "just a house", adding: "The house was used for meetings and other acts but not training."

Minister Dacic said Serbian authorities had been negotiating the release of the two staff prior to the attack.

"The kidnappers had a financial interest," Dacic said, adding that demands had been "impossible" to meet by either the families or the government.

He said Serbia would send a protest note to Washington for not informing Serbian authorities of the raid.

Diplomats and foreign nationals have been targeted in the past for kidnapping, mostly for ransom or to demand the release of Libyan fighters being held by overseas governments. Islamist militants have also targeted foreigners.

Serbia has ties with both the internationally recognised Libyan government based in the eastern town of Tobruk and with the self-declared authorities in the capital Tripoli.