AMMAN (Reuters) - Syrian government warplanes struck rebel outposts near the Jordanian border early on Tuesday, rebels said, bringing the war closer to Syria’s U.S.-allied neighbor to the south.

The air strikes, at around 3 a.m. (0000 GMT) were the first near that part of the border, a Jordanian official said. They came hours after Syria’s foreign minister warned Jordan against sending troops into his country.

Western-backed rebel groups fighting under the banner of the Free Syrian Army (FSA)’s so-called Southern Front have been active recently in the desert area near the borders with Jordan and Iraq, fighting Islamic State.

“The Syrian regime’s jets conducted four strikes against us,” said Tlas al-Salameh, the commander of Osoud al-Sharqiya, a Western-backed FSA faction which is the largest group operating in the Syrian Desert bordering Jordan.

Salameh said one air strike hit a border area where the rebel group shelters families of its fighters, others hit a rebel outpost 8 km (5 miles) from the Rukban camp where more than 80,000 refugees are stranded.

Salameh, whose group was hit by Russian bombers last year in an attack that angered the Pentagon and Jordan, said there were no casualties from Tuesday’s raids.

Salameh said the rebels had retaliated by firing rockets at Khalhala military airport, northeast of the government-held city of Sweida.

The Syrian military could not immediately be reached for comment.

The FSA groups financed and equipped by a Western and Arab operations room in Amman have been given more support in recent weeks in the campaign to drive out Islamic State from the area, Western intelligence sources say.

The U.S. has expanded the rebels’ Tanf base, further east along the border, which rebels and Western intelligence sources expect will be used as a launchpad for any assault on the IS stronghold of Bukamal on the Syrian-Iraqi border.

The rebels have succeeded in recent weeks in routing Islamic State from swathes of territory in the area, including former stronghold Bir Qassab.

The militants are believed to have regrouped further northeast in the direction of Deir al-Zor, according to Western and Jordanian intelligence sources.

The Syrian army, aided by Iranian-backed militias, has also in the last week stepped up a campaign to seize areas held by Islamic State in the Syrian Desert in a race with the FSA to grab territory the militants have retreated from.

Salameh said heavy fighting with the Syrian army was taking place in the Sabaa Biyar area where he said the army was trying to capture territory on the Damascus-Baghdad route that is mostly in the hands of Islamic State.