Syrian security forces have shot dead at least 400 civilians in their campaign to crush month-long pro-democracy protests, Syrian human rights organization Sawasiah said on Tuesday.

The group, founded by jailed human rights lawyer Mohannad al-Hassani, said the UN Security Council must convene to start proceedings against Syrian officials in the International Criminal Court and "reign in the security apparatus."

"This savage behavior, which is aimed at keeping the ruling clique in power at the expense of a rising number of civilian lives, calls for immediate international action beyond condemnations," Sawasiah said in a statement.

"The murderers in the Syrian regime must be held accountable. The rivers of blood spilled by this oppressive regime for the past four decades are enough," the statement said.

Sawasiah's board includes Syrian philosophy professor Sadeq Jalal al-Azem, whose book "Self-criticism after the defeat" helped set the stage for a revival in Arab political thought after Israel's victory in the 1967 Middle East War.

Separately, the Syrian Observatory for Human Rights, said security police arrested rights campaigner Qassem al-Ghazzawi on Tuesday in his home city of Deir al-Zor in Syria's impoverished east after protests intensified in the region last week.

The Observatory also said Mahmoud Issa, a campaigner and former political prisoner arrested last week in the city of Homs, was referred to a military court on Tuesday on charges of "possessing a Thuraya satellite phone and an advanced computer."