US President Barack Obama ISIS Islamic State
President Barack Obama confirmed the US had deployed airstrikes against the Khorasan group in Syria Reuters

President Barack Obama has confirmed that as part of military operations against Islamic State (formerly known as Isis) jihadists, US air forces also hit a separate Islamist militant group operating in Syria that threatened America's security.

"Last night we also took strikes to disrupt plotting against the United States and our allies by seasoned al-Qaida operatives in Syria known as the Khorasan group," Obama said, speaking from the south lawn of the White House.

"Once again it must be clear to anyone who would plot against America and try to do America harm that we will not tolerate safe havens for terrorist who threaten our people."

A US military spokesman said the group was planning an "imminent attack" against western targets, and had been involved in recruiting Americans and European nationals.

"Intelligence reports indicated that the Khorasan Group was in the final stages of plans to execute major attacks against western targets, and potentially the US homeland," Lt. Gen. William C. Mayville said.

Led by Muhsin al-Fadhli, a senior al-Qaida operative who was close to Osama bin Laden, the Syria-based group is believed to be made up of battle-hardened al-Qaida members from the Middle East, South Asia and North Africa.

Its presence in Syria was reported earlier this month, as it was alleged that the group is working with al-Qaida affiliates in Yemen to plot bomb attacks on US aviation.

Khorasan is believed to be a splinter group of Jabhat al-Nusra, an al-Qaida-backed jihadist group that has long been involved in the Syrian civil war.

In his speech, Obama also confirmed that for the first time US armed forces began strikes against IS, also on Syrian soil.

The president said that the military operation will continue in both Syria and Iraq "so that these terrorists can't find a safe haven anywhere."

Obama underscored that a number of Middle East nations were actively taking part in the military coalition against the jihadist group.

"We were joined in this action by our friends and partners, Saudi Arabia, the United Arab Emirates, Jordan, Bahrain and Qatar. America is proud to stand shoulder to shoulder with these nations on behalf of our common security," Obama said.

"The strength of this coalition makes it clear to the world that this is not America's fight alone."