U.S. airstrikes killed an estimated five Islamic State of Syria and Iraq (ISIS) fighters in Libya, CBS News' David Martin reports.

The fighters were apparently retrieving weapons from a weapons cache. A truck was also destroyed.

The two strikes on Tuesday targeted ISIS fighters about 100 miles southeast of the coastal city of Sirte, the U.S. Africa Command said Thursday.

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The U.S Africa Command announced on Sunday the first airstrikes in Libya since President Trump took office in January. On Sept. 22, U.S. forces conducted six precision airstrikes on a camp 150 miles from Sirte, killing 17 ISIS fighters and destroying three trucks, the U.S. Africa Command said. The camp was used by ISIS to move fighters in and out of the country; stockpile weapons and equipment; and to plot and conduct attacks, the U.S Africa Command said.

Hundreds of ISIS militants are believed to have fled Sirte into the Libyan interior after their defeat last year by militias loyal to a U.N.-backed government in Tripoli, the capital.

A Libyan official said Thursday that authorities have arrested a man suspected of taking part in the ISIS' beheading of 21 Egyptian Coptic Christians in Libya in 2015, an official said Thursday.

Chief Prosecutor Al-Sadiq al-Sour told reporters the beheadings took place behind a seaside hotel in Sirte.

"The individuals involved in the beheading are known to us by name," he said, adding that search operations are underway. He said authorities have also learned where the bodies were buried.

Al-Sour said security forces have also detained militants who were involved in the 2012 attack on the U.S. Embassy in Benghazi, which killed Ambassador Chris Stevens and three other Americans. He did not provide further information on the number of attackers arrested or their role in the hours-long assault by dozens of gunmen.

The 2012 attack took place before the emergence of ISIS and was blamed on other extremists. Al-Sour said many of the attackers later joined ISIS.

Al-Sour said at least 800 arrest warrants have been issued for suspected IS militants involved in scores of attacks across the country.

Al-Sour said the extremists have mainly entered Libya from Sudan, but have also come in through other routes. Neighboring Egypt and Tunisia have stepped up surveillance along their borders.

Libya was plunged into chaos following a NATO-backed 2011 uprising that toppled and later killed longtime dictator Muammar Qaddafi. It is split between rival parliaments, governments and militias in the east and west.