UN chief Ban Ki-moon has urged Syria's Bashar al-Assad to stop killing his own people as activists said another 11 civilians died and Damascus announced a general amnesty for crimes committed in the unrest.

Ban's comments came as Assad announced a general amnesty for crimes committed during the popular unrest that entered its eleventh month.

It said the amnesty covered infringements of the law on peaceful demonstrations, the possession of unlawful weapons and army desertion.

The opposition Muslim Brotherhood dismissed the amnesty, the third of its kind since the uprising began describing it as "neither serious nor credible."

Releasing prisoners is one of the key conditions of an Arab League roadmap approved by Syria in November to end the country's crisis, which the UN estimates has claimed more than 5,000 lives.

Opponents of Assad have said that the amnesty was meaningless because most detainees were held without charge in secret police or military facilities with no due process or legal documentation.

SANA said the amnesty for "crimes committed in the context of the events that occurred from 15 March 2011, until 15 January 2012" would run to the end of January for army deserters and people who possessed illegal arms or who violated laws on peaceful protest.

Syria's Addounia television said Arab League monitors discussed the amnesty with Damascus police today.

The amnesty was announced days before the monitors, who began work on 26 December, are due to report to the League on whether Syria is complying with an Arab League peace plan.

Under the plan, Syria's government agreed to free detainees, as well as to halt the bloodshed, withdraw the military from the streets and start a dialogue with the opposition.

Elsewhere, Qatar has proposed sending Arab troops to halt the bloodshed in Syria, where violence has raged on despite the presence of Arab League monitors sent to check if an Arab peace plan is working.

Asked by the US broadcaster CBS if he was in favour of Arab nations intervening in Syria, Qatari Emir Sheikh Hamad bin Khalifa al-Thani said "for such a situation to stop the killing ... some troops should go to stop the killing."

The emir is the first Arab leader to propose military intervention in Syria where protesters are demanding President Bashar al-Assad stand down.

His country also backed last year's NATO campaign that helped Libyan rebels topple Muammar Gaddafi.

Qatar's prime minister heads the Arab League committee on Syria and has said killings have not stopped despite the presence of Arab monitors sent there last month.