A Jordanian army official said the 12 were killed in a clash between border guards and a group of 36 people who were trying to enter Jordan from the war-torn country.

As the shooting broke out, several of the infiltrators fled back into Syria and some were wounded, he added.

Two million drug capsules were also seized, said the military official.

The Jordanian border guards acted under rules of engagement to shoot and kill anyone seeking to infiltrate the 370-km (230-mile) frontier.

Saturday's shooting was the deadliest such incident in the border area in recent memory.

Border sealed

Jordan has imposed strict border controls in recent months as part of a crackdown against Islamist extremists.

The government in Amman says it has thwarted many attempts by Islamist militants to cross from the kingdom into Syria to join the insurgency against President Bashar al Assad.

Concerns are also rising that "Islamic State" (IS) fighters may infiltrate refugee groups who regularly enter Jordan to escape the conflict.

Jordan says as many as 1.4 million Syrians have entered the country since the civil war began in 2011 and some 17,000 are currently stranded in the border area, awaiting entry.

The government has clamped down on the number of refugees, allowing just a few dozen people to cross the border daily.

The border command said it also frequently intercepts smugglers trying to cross into Jordan.

mm/rc (AFP, AP, Reuters)