Counting gets underway in a referendum on the Syrian constitution that does offer some reforms, yet could keep President Bashar al-Assad in power until 2028.

The reforms allow political pluralism and impose a presidential limit of two seven-year terms, but this limit is not retrospective - implying that Assad could serve another two terms after his current one ends in 2014.

Diplomats who toured polling stations in the capital Damascus reported seeing only a handful of voters.

Meanwhile, video uploaded to a social media website - which Reuters cannot independently verify - purports to show continued shelling of the Baba Amro district of Homs.

The speaker says this is the 24th day the city has been attacked.

An opposition activist said the bombardment began at dawn, and that two people had been killed.

The International Committee of the Red Cross has said conditions in parts of Homs are worsening by the hour, but has failed to secure a pause in the fighting to allow evacuation of the wounded and delivery of aid.

Peaceful protests in Syria began nearly one year ago, but the brutal regime response has now spawned an armed insurrection.

Nick Rowlands, Reuters