At a new round of talks next Monday, ambassadors from the 27 nation bloc will mull whether to also slap an assets freeze and travel ban on Syrian President Bashar al-Assad, the sources added.

At Friday's talks, the ambassadors agreed to "work without delay on additional restrictive measures against people responsible for violent repression against civilians, and in particular to look fully at including the highest level of the Syrian leadership on the list."

France in particular had urged that Assad be included in the list of Syrians targeted by the assets freeze and travel ban. Several smaller EU nations were more reticent.

Sanctions against the 13 other regime officials listed by the ambassadors need to be endorsed by governments and are expected to come into force by Tuesday through publication in the EU Official Journal, the diplomats said.

The 27 ambassadors also agreed a range of punitive measures, including an arms embargo.

The talks were held as activists said Syria's security forces shot dead at least five people when thousands rallied on a "Day of Defiance" against Assad's regime.

Human rights groups say more than 600 people have been killed and 8,000 have been jailed or gone missing since the protests began in mid-March.