SYRIA AND UN READY TO FIGHT ISIS.

 The Syrian regime says it's ready to accept support from the United States and others working under the U.N. umbrella to fight "terrorists."

The comments, by Syrian Foreign Minister Walid Moallem, were made Monday as ISIS fighters seized control of a strategically important air base in the country.

The war-racked nation has been losing control of the northeastern region to ISIS militants.

Moallem, however, warned against any unilateral action or strikes in Syrian territory without its permission.

"Any effort to fight terrorism should be done in coordination with Syrian government," Moallem said.

Air base seizure

The Islamic extremist group, which has taken over large areas of Syria and Iraq, wrested the Al-Tabqa air base from the Syrian military on Sunday, according to the Syrian Observatory for Human Rights, a UK-based group that monitors the conflict.

Syrian state television reported that the Syrian military had evacuated the air base in Raqqa province to regroup and was still carrying out strikes against ISIS fighters in the area.

ISIS, which refers to itself as the Islamic State, is part of the complex web of groups fighting in the long-running Syrian conflict -- a war that the U.N. estimates has killed more than 191,000 people.

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Map: Al-Tabqa air base, Syria

The spread of ISIS

Rebels have been battling the al-Assad's regime since March 2011, and the civil war has turned the country into a haven for jihadists.

ISIS has thrived amid the chaos, gaining global notoriety for its brutal tactics including the beheading of American journalist James Foley last week.

After its break with al Qaeda earlier this year, ISIS has grown in strength and reach. Its dramatic, murderous advance in northern and western Iraq this year provoked U.S. airstrikes aimed at helping Kurdish and Iraqi forces.

U.S. and Kurdish officials say ISIS is now under pressure in Iraq. But the extremist group continues to win significant victories in Syria.

Planes moved before base fell

Al-Taqba air base is the last major military base in Raqqa province, which borders Turkey, to fall into ISIS' hands. The group now is now understood to have effective control over the entire province, aside from a few villages in the south.

The warplanes from the base had already been taken to other locations before ISIS took control, the Syrian Observatory for Human Rights reported.

It said ISIS fighters were seen carrying the heads of Syrian regime soldiers. Both sides were reported to have suffered heavy losses in the battle for the base.

ISIS controls major cities in Iraq and Syria, as well as oil fields, main roads and border crossings. It also has under its control more military hardware than some national armies after seizing both Iraqi and Syrian military bases and armories.