Dozens of people were killed on Jan. 7 when a bomb hit a police training center in the worst attack since the fall of Muammar Gaddafi. (Reuters)

A powerful truck bomb exploded near a police training camp in western Libya on Thursday, killing more than 45 people in a region where the Islamic State has battled for footholds.

There was no immediate claim of responsibility for the blast in Zliten, near the Mediterranean coast about 60 miles southeast of Tripoli. But militants pledging loyalty to the Islamic State have been seeking to expand in the area.

The region also is a jumping off point for boats taking migrants to Europe. Smugglers in the past have clashed with police.

The attack also underscored the increasing lawlessness in Libya, which is divided by two rival governments and has become one of the centers for the Islamic State in North Africa.

Aftermath of a truck bombing on a police training site in Zliten, Libya, on Thursday. (Mahmud Turkia/AFP/Getty Images)

Libya’s state-run media reported at least 50 dead. Later, however, the Reuters news agency quoted Fozi Awnais, head of the crisis committee for the health ministry in Tripoli, as saying 47 people had died.

Some security and medical sources, cited by news agencies, reported counts as high as 65. The main hospital in nearby Misrata appealed for blood donations.

At least 200 people were injured in the blast — some seriously — raising the possibility the death toll could rise.

In Washington, White House press secretary Josh Earnest called the attack a “cowardly act of terrorism” and extended condolences to the victims, their families and the Libyan people.

“The United States continues to be deeply concerned about [Islamic State-inspired] terrorists carrying out acts of violence, particularly in Libya,” he said. “And that is why you’ve seen the United States take aggressive action, including inside of Libya, to take out ISIL leaders.”

The training camp is used by the border police, whose missions include trying to block smugglers attempting to take migrants on boats bound for southern Europe. Hundreds of people have drowned in the dangerous crossings.

The Zliten mayor, Miftah Hamadi, said the blast occurred as around 400 recruits were gathering.

“It was horrific. The explosion was so loud it was heard from miles away,” Hamadi told Reuters. “All the victims were young and all about to start their lives.”

Libya has been wracked by unrest and power struggles since the toppling in 2011 of the late dictator Moammar Gaddafi during Arab Spring-inspired uprisings.

The oil-rich country is now divided between a breakaway Islamist government based in the capital of Tripoli and an internationally recognized administration in the east.

Security experts estimate there are as many as 3,000 fighters loyal to the Islamic State in Libya. The country has become one of the primary locations to train with the group outside of Syria and Iraq.

Volunteers from Tunisia, Algeria, Egypt, Saudi Arabia and other countries have flocked here to fight with the extremists and other jihadist organizations. The Islamic State also has succeeded in pulling away members of other Libyan extremist groups.

Murphy reported from Washington.

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Today's coverage from Post correspondents around the world