U.S. President Barack Obama vowed more strikes against terrorists in Syria on Tuesday after US forces carried out separate air raids targeting the ISIL militants and an al-Qaeda affiliate groups.

U.S. President Barack Obama vowed more strikes against terrorists in Syria on Tuesday after US forces carried out separate air raids targeting the militants of so-called 'Islamic State of Iraq and the Levant' (ISIL) and an al-Qaeda affiliate groups that Washington said was plotting attacks on America and Europe.

"We will not tolerate safe havens for terrorists who threaten our people," Obama said as he left the White House to travel to the United Nations in New York, where he will meet officials from Arab nations that joined in the strikes against the ISIL group.

Speaking just hours after he launched the air strikes, Obama said the coalition "represents partners and friends with which we have worked for many, many years to make sure that security and prosperity exists in this region."

Flanked by Secretary of State John Kerry and national security advisor Susan Rice, Obama told the leaders of Bahrain, Jordan, Qatar, Saudi Arabia, the United Arab Emirates and Iraq he was "very appreciative" of their help.

He praised them "all for their participation and commitment to rolling back the violent extremism that has so disrupted Iraq and Syria and friends in the region as a whole."

The White House said US forces made separate strikes on its own against the Khorasan group, an al Qaeda affiliate, in order to disrupt planning for imminent attacks on the west.

US and Arab strikes on militant targets in Syria overnight were just a start of a coalition effort to weaken ISIL, an extremist group that has killed thousands and beheaded at least three westerners while seizing control of parts of Syria and northwestern Iraq.

"I can tell you that last night's strikes were only the beginning," Rear Admiral John Kirby, the Pentagon press secretary, told reporters. He said the strikes had been 'very successful' and would continue.

Another military spokesman said Arab nations, including Saudi Arabia, Jordan, Bahrain and the United Arab Emirates, took part in the second and third waves of attacks.

Lieutenant General William Mayville Jr. said the actions by those Arab countries ranged from combat air patrols to hitting targets.

Mayville said the strikes hit training camps, headquarters, vehicles and other sites under the control of ISIL. He said the strikes were the start "of a credible and sustainable persistent campaign to degrade and ultimately destroy" ISIL.

Obama said he would meet with Iraqi Prime Minister Haider al-Abadi and "friends and allies" at the United Nations to continue building support for the coalition against the ISIL group.

The US leader said the strength of the coalition, now at more than 40 countries, showed the fight against such militants is not America's alone.

"The overall effort will take time. There will be challenges ahead but we're going to do what's necessary to take the fight to this terrorist group," Obama said.

Obama said the campaign is in line with the strategy he outlined earlier this month to combat ISIL.