Jordan has foiled a major plot by an Al-Qaeda linked cell, which aimed to destabilise the key US ally's security by bombing shopping centres and assassinating Western diplomats, state television has said.

Security forces detained 11 suspects in connection with a plot going on since June to carry out attacks in the capital Amman using smuggled weapons and explosives brought from Syria, according to security officials cited by television.

"Their plans included getting explosives and mortars from Syria," said a security source.

The attacks, aimed at western and commercial areas, would likely have resulted in the death of thousands, according to Jordanian authorities.

The security source said the suspects had manufactured explosives "aimed at inflicting the heaviest human losses possible."

Jordan is a key US ally in the Middle East and Israel's peace partner.

The Arab kingdom has often been targeted by Al-Qaeda and other Islamic militants.

It regularly arrests terror suspects and puts them on trial.