State television in Syria is reporting that at least nine people have been killed and nearly 30 others wounded in an explosion in the capital, Damascus.

The apparent suicide bomb attack occurred close to a mosque in the city centre after Friday prayers.

UN leader Ban Ki-moon sayst the Syrian government is "in contravention" of an agreed peace plan by keeping troops and heavy weapons in cities.

Mr Ban also said he is "gravely alarmed" by reports of shelling of populated areas in the country.

Bashar al-Assad's government had agreed a troop withdrawal from cities as part of a six-point peace plan agreed with UN-Arab League envoy Kofi Annan.

The truce officially started on 12 April but has barely held.

It is to be monitored by 300 UN observers due to arrive in Syria in coming weeks.

Reports from Syria cannot be independently verified as state authorities have barred international journalists and rights groups.

The UN says more than 9,000 people have died since a revolt began against President Assad's regime in March last year.