In this US Air Force file photo a MQ-1B Predator remotely piloted aircraft flies overhead in Nevada. AFP

The US army said Thursday it carried out a drone strike against Al Qaeda leaders in northwestern Syria near the Turkish border, killing 17 ‘militants’, according to a war monitor.

The Syrian Observatory for Human Rights said five civilians were also among those killed.

"US Forces conducted a strike against a group of Al Qaeda in Syria (AQ-S) senior leaders meeting near Idlib, Syria," said Major Beth Riordan, the spokeswoman for United States Central Command (CENTCOM).

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"The removal of these AQ-S leaders will disrupt the terrorist organisation's ability to further plot and carry out global attacks threatening US citizens, our partners and innocent civilians," Riordan said in a statement.

She did not specify the number of deaths from the strike.

A US Air Force MQ-9 Reaper remotely piloted aircraft as it awaits an engine test prior to Intelligence. Michael Mason/AFP

But the Britain-based Observatory said the operation, which targeted a dinner meeting of militants in the village of Jakara in the Salqin area, killed at least 17 militants including 11 leaders.

The village lies in Syria's last major rebel bastion of Idlib, which is dominated by the Hayat Tahrir Al Sham (HTS) group, led by a former Al Qaeda affiliate, and its rebel allies.

But other militant groups, including the rival Al Qaeda-linked Hurras Al Deen faction, are also present in the area.

Observatory chief Rami Abdel Rahman said that five non-Syrian militants were among those killed, but their nationalities were not immediately known.

"They had been invited to dinner in a tent on a farm in Jakara," he said.

"It was a meeting of leaders opposed to HTS and who reject the Russia-Turkish deals" that led to a fragile truce in Idlib, he said. "Some were close to Hurras Al Deen."

A March agreement between rebel backer Ankara and government ally Moscow halted a deadly offensive by government forces against the region of some three million people.