CAIRO — Two Serbian hostages were killed in US airstrikes against an Islamic State training camp in western Libya on Friday, Serbia’s officials said Saturday.

The strikes by US F-15 jets against a compound in Sabratha, 50 miles west of Tripoli, the capital, killed at least 43 people, according to Libyan officials. The Pentagon said it believed that the main target of the attacks, Noureddine Chouchane, a Tunisian militant who was accused of facilitating two major attacks on Western tourists in Tunisia last year, was among the dead.

But the deaths of the hostages, both Serbian Embassy employees, confirmed first by a Libyan militia group and then by Serbia’s prime minister, drew protests from Serbia and raised questions about the quality of the US intelligence that led to the strikes.

At a news conference in Belgrade, the Serbian capital, the foreign minister, Ivica Dacic, said the two Serbs — identified as Sladjana Stankovic, a communications officer, and Jovica Stepic, a driver — were taken hostage Nov. 8 when their three-vehicle convoy was attacked as it passed through Sabratha.

The convoy was traveling to Tunisia when the attack, which was one of the first overt signs of the Islamic State’s presence in the town, occurred. Serbia’s ambassador to Libya, who was traveling in a separate vehicle with his wife and two sons, ages 8 and 14, escaped unharmed.

Dacic said the Serbian authorities were still negotiating for the hostages’ release when a barrage of US missiles slammed into the compound outside Sabratha early Friday. “The kidnappers had a financial interest,’’ Dacic told reporters, according to Reuters.

Dacic said the Islamic State’s demands for the release of the two men had been “impossible’’ to meet. Nonetheless, the Serbian government was angry that it had not been informed of the raid in advance, and will send a protest note to Washington, he said.

Although the Libyan authorities in Tripoli have not officially notified Serbia of the hostages’ deaths, an armed group that controls the capital’s only functioning airport posted a photograph on Facebook that showed two coffins next to a small plane that were said to hold the Serbs’ remains.

US officials said the missile attack Friday killed at least 30 Islamic State militants, mostly from Tunisia, as they slept. US surveillance indicated that they had been training at the compound for weeks, apparently in preparation for an attack in the region.

Kidnapping for ransom is rife in much of Libya, where the rule of law has collapsed.