Syrian rebels repelled on Sunday a suicide attack by Islamic State militants on a military base near a border crossing into Iraq and a rebel convoy headed to the base, leaving at least four dead and several injured, rebel sources said.
The midnight attack on a heavily defended base near the al Tanf border crossing involved at least one explosive-laden vehicle that rammed an entrance to the base. At least two people were killed and scores wounded, a rebel source said.
The militants also staged a suicide attack on a convoy of rebel fighters from the Western-backed Osoud al Sharqiya rebel group, who had sent reinforcements from their outpost near the Rukban refugee camp further south-west. Two of their fighters were killed in the ambush.
Islamic State "staged a suicide attack and there were clashes inside Tanf. Two were killed and several injured. They also attacked our convoy but it's over and matters are under control," said a senior rebel source from Osoud al Sharqiya who requested anonymity.
U.S.-led coalition planes were involved in the operation, which went on into the early hours of dawn, to track down the militants who staged the hit-and-run attack and apparently fled, a rebel commander involved in the operation said.
Both Tanf and Rukban are near the joint Syria-Iraq-Jordan border. Osoud al Sharqiya, one of the main groups in that area fighting Islamic State militants, is part of the Free Syrian Army of rebels financed and equipped by a Western coalition.
Jordan, a U.S. ally, backs the moderate rebel groups aligned with the so-called Southern Front supported by an Arab-Western coalition, who trying to prevent opposition-held southern Syria from falling to Islamic State.
The rebels took the border crossing of Tanf last year from the ultra-hardline militants and tried unsuccessfully to drive the militants out of the Syrian border town of Bukamal on the Euphrates, further north-east, a major supply conduit for the militants between their strongholds in Iraq and Syria.
In recent weeks, the militants in the Syrian desert near the Jordanian border have regrouped further north to reinforce their Raqqa stronghold, after major defeats in Syria and Iraq.
Western intelligence sources have worried for months that militants fleeing from their main urban strongholds of Raqqa in Syria and Mosul in Iraq could find a safe haven in the region.
A Western intelligence source told Reuters that U.S. and British special forces are expanding the Tanf base to use it as a major launching pad for operations in coming months to oust militants from Bukamal, a major militant stronghold.
Diplomats say plans are underway to stage new coalition strikes on Islamic State fighters in the south, including an area to the west of the southern city of Deraa. Militants entrenched in the Yamouk River Valley near the Israeli border have recently made gains.