A war monitor has reported that the Jordanian air force launched strikes in Syria in January and December as Amman pursues efforts to fight drug smuggling.

Amman has not confirmed it carried out the raids, although it had previously vowed to fight the narcotics trade in cooperation with war-torn Syria.

In Damascus's first comments on the strikes, the foreign ministry said: "Syria deeply regrets Jordanian Air Force strikes on... Syrian territory".

"There is no justification for such military operations inside Syrian territory," it said.

It added that Syria wanted to avoid "causing tensions or affecting the continued restoration of brotherly ties between the two countries".

One of the main drugs smuggled out of Syria is the amphetamine-like stimulant captagon, for which there is huge demand in the oil-rich Gulf.

Captagon is now by far Syria's biggest export, dwarfing all its legal exports put together, according to estimates drawn from official data by AFP.

Talks between Jordanian Foreign Minister Ayman Safadi and Syrian President Bashar al-Assad established a forum to combat drug smuggling from Syria, which held its first meeting in Amman in July.

But Jordan's strikes were not consistent with what was agreed on by both sides, the foreign ministry said.

Damascus "has expressed its readiness to cooperate with Jordanian civil and security institutions, but those messages were ignored," it added.

On January 18, at least nine civilians, including two children, were killed in suspected Jordanian air strikes in Sweida province against drug traffickers, the Syrian Observatory for Human Rights war monitor reported.

Jordan was reportedly behind air strikes in Syria on December 18 that killed five people, including a woman and two children.

On Tuesday, the Observatory also said the bodies of six smugglers killed in clashes with Jordanian forces earlier this month had been found in Syria's south.

Fighting drug trafficking from Syria was one of the main issues that drove regional re-engagement with Assad's government, which was re-admitted to the Arab League in May after more than a decade of isolation.

Since 2011, Syria has endured a bloody conflict that has claimed more than half a million lives and displaced several million people.