The Syrian Observatory for Human Rights monitor said the blasts in the Kisweh area, south of the Syrian capital, may be the result of an Israeli air strike.

The Israeli military, which has struck many military sites in Syria since Assad's fall, told AFP in Jerusalem it did not attack the site.

The Britain-based Observatory, which has a network of sources in Syria, said that "loud blasts resonated in the wider capital area".

The explosions occurred "at ammunition depots of the former regime forces... near the town of Kisweh", sending a thick cloud of smoke billowing over the site, the Observatory said.

An AFP video journalist saw small fires burning in the blackened rubble of a flattened building on the outskirts of the town of Kisweh. Several other one-storey buildings stood undamaged nearby.

The explosions continued into Sunday evening, ringing out across surrounding areas, the journalist said.

Israel, which rarely comments on its actions in neighbouring Syria, has carried out hundreds of air strikes on military sites since Islamist-led forces ousted Assad and seized Damascus last month.

Israel has said it was seeking to prevent weapons from falling into hostile hands.

Most recently, the Observatory said Israeli war planes hit sites of the now defunct Syrian army in the Aleppo area on Friday.

In late December, the Observatory said 11 people died in an explosion at an arms storage facility in the Adra area northeast of Damascus, adding that it was possibly the result of an Israeli strike. Israel denied any involvement.