Jordan said on Tuesday it had downed a drone carrying drugs from Syria into its northern region, and it said it would not allow the border area to become a front line in an Iran-linked drug war.

The kingdom has blamed pro-Iranian militias, who it says are protected by units within the Syrian army, for smuggling drugs across its borders towards lucrative Persian Gulf markets.

Damascus says it is doing its best to curb smuggling and continues to bust smuggler rings in the south. It denies complicity by Iranian-backed militias linked to its army and security forces.

"We are continuing to deal with resolve and force with any threat to our borders and any attempt to destabilize the security of the nation," the Jordanian army said in a statement.

The plane, which was carrying crystal methamphetamine, was intercepted and downed on Jordan's side of the border, it said.

War-torn Syria has become the region's main site for a multi-billion-dollar drug trade, for a Syrian-made amphetamine known as captagon.

Jordanian officials say they have raised their concerns with Syrian authorities, and although they have received pledges they say they have not seen any real 

Amman carried out rare air strikes on southern Syria last month, hitting an Iran-linked drugs factory and killing a smuggler allegedly behind big hauls. 

The bombing was a message to Damascus as it was involved in an Arab effort to end Syria's estrangement, officials said.

Jordan requested more US military aid to bolster security on the border, where Washington has given around $1 billion to establish border posts, officials say.

Hezbollah also denies involvement in the drugs trade and says Jordan's allegations echo Washington's campaign to undermine Iran's influence in the region.