REUTERS - The United States said it conducted air strikes on Wednesday night against the so-called Khorasan Group of Al-Qaida-linked militants based in Syria, saying the group was plotting to attack Europe or the United States.

"We took decisive action to protect our interests and remove their capability to act," U.S. Central Command said in a statement on Thursday.

It said the strikes, carried out by the U.S. military against five Khorasan targets, "resulted in the intended effects by striking terrorists."

The air strikes also hit the group's vehicles and buildings as well as bomb-making and training facilities, according to the statement. An earlier U.S.-led air strike aimed at the group in September is believed to have failed to kill one of its top leaders as had been hoped by Washington.

Veteran Al-Qaida fighters

While the Islamic State group is getting the most attention now, another band of extremists in Syria - a mix of hardened jihadis from Afghanistan, Yemen, Syria and Europe - poses a more direct and imminent threat to the United States, working with Yemeni bomb-makers to target U.S. aviation, American officials say.

At the center is a cell known as the Khorasan group, a cadre of veteran Al-Qaida fighters from Afghanistan and Pakistan who traveled to Syria to link up with the Al-Qaida affiliate there, the Nusra Front.

But the Khorasan militants did not go to Syria principally to fight the government of President Bashar Assad, U.S. officials say. Instead, they were sent by Al-Qaida leader Ayman al-Zawahiri to recruit Europeans and Americans whose passports allow them to board a U.S.-bound airliner with less scrutiny from security officials.

In addition, according to classified U.S. intelligence assessments, the Khorasan militants have been working with bomb-makers from Al-Qaida's Yemen affiliate to test new ways to slip explosives past airport security. The fear is that the Khorasan militants will provide these sophisticated explosives to their Western recruits who could sneak them onto U.S.-bound flights.

The Obama administration has said that the Islamic State group, the target of more than 150 U.S. airstrikes in recent weeks, does not pose an imminent threat to the continental U.S. The Khorasan group, which has not been subject to American military action, is considered the more immediate threat.