The Libyan branch of ISIS staged a gruesome attack Wednesday on government-security headquarters in the western city of Sabratha. According to the AP, the group beheaded 12 officers before taking control of the complex.

“A second security official said that the militants used the headless bodies of the officers they killed to block the roads leading to the security headquarters—which they occupied for about three hours,” the report added.

The attack came less than a week after American airstrikes hit an ISIS training camp in the city, killing about 40 people, including two Serbian hostages. The renascent U.S. efforts in Libya speak to a growing concern shared by a number of countries about ISIS’s increasing ability to flourish in the North African country.

American intelligence officials estimate that the group’s ranks in Libya have grown to 6,500 fighters, more than doubling since the fall. ISIS first declared its intentions to establish a presence in Libya in 2014 and has been launching attacks ever since. The group is now thought to control 150 miles of Libyan coastline.

Part of this surge is being attributed to the civil discord in Libya among the country’s competing political factions and militias, which have produce rival governments with their own security forces. The chaos has had major economic repercussions as well. Last month, the head of the country’s national oil company estimated that Libya has lost $68 billion in oil sales since 2013.

With Islamic State fighters suffering under heavy fire in Iraq and Syria, the group’s strategy of exploiting the security vacuum in Libya also appears to be a conscious one.

“Islamic State leaders in Syria are telling recruits traveling north from West African nations like Senegal and Chad, as well as others streaming up through Sudan in eastern Africa, not to press on to the Middle East,” The New York Times reported. “Instead, they are being told to stay put in Libya.”

Although it’s not the most commonly used country, Libya is a popular place from which migrants and refugees cross the Mediterranean to go to Europe. One harrowing possibility for Western countries is the growth of ISIS in Libya means Europe, given its proximity, could be more vulnerable to attacks.

On Wednesday, the French daily Le Monde issued a report chronicling France’s enhanced military engagement in Libya, which the paper characterized as a “secret war” to stanch the group’s growth in the wake of ISIS’s attacks on Paris in November. Italy and the United Kingdom are also thought to be contemplating military involvement.

The presence of special forces from these three countries as well as the United States have been reported in recent weeks and last month. Italy discreetly agreed to allow U.S. drones operating in Libya and North Africa to launch from one of its bases after a year of negotiations.

But a complicated and telling question, which The Guardian noted on Tuesday, is how a major coordinated military operation could legally come together at all if deemed necessary.

With a UN mandate highly unlikely at this point – because that would require Russia’s approval – there would need to be an official request from Libyan authorities themselves. But there is no agreement in Libya on who the government is.

Since the American-led intervention in 2011 that resulted in the ouster of Muammar al-Qaddafi, the longtime leader, the U.S. has intermittently deployed troops for operations in Libya. The most recent confirmed activity took place in December of last year, less than 18 months after American commandos seized Ahmed Abu Khattala, the man currently on trial for his alleged role in the 2012 Benghazi attacks that killed four Americans, including Ambassador Chris Stevens.

President Obama says he will go after ISIS “wherever it appears,” and is reportedly considering whether to approve the broader use of military force to combat the group in Libya. And, as he said last week: “We will continue to take actions where we’ve got a clear operation and a clear target in mind. As we see opportunities to prevent ISIS from digging in, in Libya, we take them.”