The UN and Arab League's envoy to Syria, Kofi Annan, has said he has held "constructive and candid" talks with President Bashar al-Assad in Damascus, BBC reports.

Mr Annan admitted on Saturday that the international community's efforts to find a political solution to the escalating violence had not succeeded.

A ceasefire was supposed to begin in mid-April as part of his peace plan.

Mr Assad earlier said the main obstacle was foreign countries giving political support and weapons to "terrorists".

Meanwhile, activists said security forces were shelling parts of the cities of Deir al-Zour, Deraa, Homs, Aleppo and Damascus on Monday. More than 100 people were killed on Sunday, most of them civilians, they added.

Monday's talks in Damascus were "constructive and good", Syrian foreign ministry spokesman Jihad al-Makdisi wrote on Twitter afterwards, echoing Mr Annan's comments to reporters.

Discussions focused on the implementation of the former UN secretary general's six-point peace plan, Mr Makdisi added.

Mr Makdisi said both men considered the recent Action Group on Syria meeting in Geneva an important step towards creating an environment for national dialogue and a political solution to the crisis.

The Action Group urged all parties to recommit to a sustained cessation of armed violence and the immediately implementation of Mr Annan's initiative. It also called for the creation of a transitional government formed on basis of mutual consent, which could include officials serving under President Assad and opposition members.

Mr Annan spent the night at the hotel in the Syrian capital where unarmed UN military observers have been staying since suspending their ceasefire monitoring mission last month because of the continuing violence.