US and Arab warplanes hammered Islamic State militants in eastern Syria early Tuesday, opening a new front in the fight against the jihadist group, defense officials said.

Bahrain, Jordan, Qatar, Saudi Arabia and the United Arab Emirates took part in the bombing raids, US media reported, in an extraordinary show of Arab solidarity against the IS group that has rampaged through Syria and Iraq.

A US defense official, who spoke on condition of anonymity, confirmed to AFP that Arab "partners" joined the bombing runs but did not say which countries were involved.

The US-led air assault in Syria marks a turning point in the war against the IS group, as the administration of US President Barack Obama had long been reluctant to intervene in Syria's raging civil war.

But Washington concluded it had to act and convinced Arab allies to join in, amid fears IS fighters could wreak havoc across the region and eventually stage terror attacks in Europe or the United States if left unchecked.

"I can confirm that US military and partner nation forces are undertaking military action against ISIL (Islamic State group) terrorists in Syria using a mix of fighter, bomber and Tomahawk Land Attack Missiles," Pentagon spokesman Rear Admiral John Kirby said in a statement.

The decision to conduct the air strikes was undertaken on Monday by the head of US Central Command, General Lloyd Austin, "under authorization granted him by the commander in chief," Kirby said.

"We will provide more details later as operationally appropriate."

The strikes focused on IS positions in Raqa, a stronghold for the Sunni extremists, as well as targets along the Iraq-Syria border, according to a second Pentagon official, who spoke on condition of anonymity.

US F-22 fighter jets, America's most sophisticated warplane, were scheduled to take part in the raids as well -- the first combat mission for the costly aircraft, the second official said.

Along with "ongoing" air raids, the US military fired Tomahawk cruise missiles from warships in the Gulf and Red Sea, the official said.

A senior White House official told AFP that Obama was "being updated on the operation" in Syria.

US media said the president had spoken to Congressional leaders about the strikes.

- 'No safe haven' -

The wave of strikes came less than two weeks after Obama warned that he had approved an expansion of the campaign against the Islamic State group to include action in Syria.

"I have made it clear that we will hunt down terrorists who threaten our country, wherever they are," Obama said on September 10 in a speech to the nation.

"This is a core principle of my presidency: if you threaten America, you will find no safe haven."

Under Obama's orders, US warplanes began air strikes against IS targets in Iraq on August 8, with about 190 raids carried out against the extremists there.

Obama, however, has repeatedly promised the campaign would not involve a combat mission for US ground troops in Iraq.

France is the only country to have joined the US air strikes against the IS in Iraq. Australia said Monday it was deploying fighter jets to join the campaign.

The US president's strategy calls for American air power combined with training and arming local forces in Iraq and "moderate" rebel fighters in Syria.

His approach has sparked criticism in Washington and the Middle East that the effort will fail without capable ground forces that can roll back the well-organized and well-financed jihadists.

Last week, the US Congress endorsed Obama's plan to train and arm moderate Syrian rebels to battle the IS group, which has beheaded two American journalists, James Foley and Steven Sotloff.

Lawmakers on the left, wary of the United States plunging into another open-ended war in the Middle East, have vowed to hold broad use-of-force debates later this year following the November 4 midterm elections.

The air strikes in Syria came as Kurdish militia fought to defend a key border town in northern Syria, after 130,000 terrified residents fled to Turkey to escape an IS jihadist advance.

US military has large force arrayed across Mideast
Washington (AFP) Sept 23, 2014 - Having expanded its air war against Islamic State jihadists into Syria, the US military can draw on a vast arsenal of aircraft, troops and hardware across the Middle East.

Here are the basic facts on the American military presence in the region and the strikes carried out so far, according to the Pentagon and defense analysts:

- Troops in the Middle East -

There are roughly 35,000 US troops deployed in the Middle East outside Iraq, including about 15,000 in Kuwait, 7,500 in Qatar, 6,000 in Bahrain, 5,000 in the United Arab Emirates and 1,000 in Jordan. There are also reportedly teams of CIA officers in Jordan helping train Syrian rebel forces along with other Western and Arab intelligence agents.

- Iraq -

There will soon be 1,600 US troops deployed in Iraq, including an additional 475 personnel ordered in by President Barack Obama this month.

Roughly 600 troops in the US contingent are serving as "advisers" to Iraqi government and Kurdish forces, coordinating air raids. Some are based at joint operation centers in Baghdad and in northern Iraq.

The remaining US forces mostly are devoted to securing the US embassy and its diplomats.

- Aircraft -

Estimates vary but the United States can draw on dozens of aircraft stationed in the region, including F-15, F-16 and F/A-18 fighter jets, F-22 stealth Raptors, armed Reaper drones, B-1 bombers, attack helicopters, various surveillance aircraft and aerial refueling tankers.

The F/A-18 Super Hornets are flying off of the aircraft carrier USS George H.W. Bush in the Gulf and warplanes will soon start flying out of Arbil airfield in northern Iraq's Kurdish region.

In addition, US warships in the Gulf and elsewhere are equipped with Tomahawk cruise missiles that can travel at subsonic speeds and hit a target more than 1,500 miles (2,500 kilometers) away.

- Regional bases -

US aircraft bombing IS militants in Iraq are reportedly flying out of al-Dhafra Air Base in the United Arab Emirates, Ali al-Salem Air Base in Kuwait and al-Udeid Air Base in Qatar, which is also home to a vital US air combat command center for the region.

At the Combined Air Operations Center (CAOC) in Qatar, US officers oversee airspace authority, air defenses and electronic warfare in 20 regional countries. The Qatar air base, with a 15,000-foot runway and a significant supply of munitions, is a crucial logistical hub.

US F-16 fighter jets also have been stationed in Jordan since last year and the Pentagon has basing agreements with Oman. In addition, the US military can use a base in Diego Garcia for B-52, B-1 and B-2 flights.

In southern Turkey, US crews have long operated out of Incirlik and about 1,500 airmen are stationed there. Some media reports say the United States is flying surveillance planes out of the base but that Ankara is unwilling to approve bombing missions.

- Air strikes in Iraq -

Since August 8, there have been 190 US air strikes carried out in Iraq, from south of Baghdad to Haditha dam in the west to Kurdish areas in the north.

Many of the strikes targeted jihadists in the country's north fighting for control of the strategic Mosul dam, according to Central Command.

The strikes around Mosul helped Iraqi and Kurdish troops retake the dam, which the IS jihadists briefly held, but fighting has nevertheless raged on in the area.

After Mosul, the most frequent targeted area during the first month of strikes was around Arbil. Other strikes focused on another massive dam, near Haditha in the west, a crucial part of Iraq's infrastructure.