Syria was under growing pressure on Thursday to stop using military force against anti-government protesters after the US slapped sanctions on President Bashar Al-Assad over human rights violations.

Broadening its campaign against pro-democracy rallies, Syrian tanks have been shelling a border town for days in the latest attempt to crush a revolt against Al-Assad's 11-year rule.

Western powers have condemned Al-Assad's crackdown on two months of unrest which has killed at least 700 civilians, according to human rights groups.

Washington's decision to target Al-Assad personally with sanctions raises the stakes in the conflict and poses questions about whether the West may ultimately seek his overthrow.

Leading Syrian opposition figure Haitham al-Maleh said the decision meant 'members of the regime are now under siege'.

'Any move by the international community may help the Syrian people in continuing their uprising,' he told Reuters from Damascus.

The Treasury Department said it would freeze any of the assets owned by Syrian officials in the US or which fall within US jurisdiction, and bar US individuals and companies from dealing with them.

The sanctions list also includes Vice President Farouq al-Shara, Prime Minister Adel Safar, Interior Minister Mohammad Ibrahim al-Shaar, Defence Minister Ali Habib plus Abdul Fatah Qudsiya, head of Syrian military intelligence, and Mohammed Dib Zaitoun, director of the political security directorate.

'The actions the administration has taken today send an unequivocal message to President Al-Assad, the Syrian leadership and regime insiders that they will be held accountable for the ongoing violence and repression in Syria,' Acting Under Secretary for Terrorism and Financial Intelligence David S Cohen said in a statement.

An EU diplomat said the European Union was expected to extend sanctions on Syria next week to include Al-Assad as well. 'What I detect from members states...is that there is a clear majority, if not now a consensus, for putting him on the list,' the diplomat told Reuters.

Reforms

The unrest in Syria began two months ago when protesters, inspired by uprisings in other parts of the Arab world, took to the streets calling for greater freedoms. The crackdown by troops, security forces and irregular Al-Assad loyalists led them to go further and demand an end to Al-Assad's rule.

Syrian authorities blame most of the violence on armed groups backed by Islamists and outside powers who they say have killed more than 120 soldiers and police.

A senior US official said the new sanctions were meant to force Al-Assad to carry out promised political reforms.

'President Al-Assad has a clear choice: either to lead this transition to democracy or to leave,' the official, speaking on condition of anonymity, told reporters.

Switzerland said on Wednesday it would impose travel bans on 13 top Syrian officials -- but not Al-Assad himself -- and freeze any of their assets held in Swiss banks, matching a decision by the EU last week.

Last month, Washington imposed a first round of sanctions on two relatives of Al-Assad and the country's intelligence agency for alleged human rights abuses.

Syria has barred most international media from operating in the country, making it hard to verify reports from activists and officials.

On Saturday, Syrian troops went into Tel Kelakh -- a day after a demonstration there demanded 'the overthrow of the regime', the slogan of revolutions that toppled Arab leaders in Egypt and Tunisia and challenged others across the Middle East.

'We're still without water, electricity or communications,' a resident of Tel Kelakh said by satellite phone.

He said the army was storming houses and making arrests, but withdrawing from neighbourhoods after the raids. In a sign that the army was coming under fire in the town, he said some families 'are resisting, preferring death to humiliation'.

A witness on the Lebanese side of the border said heavy gunfire could be heard from nearby Tel Kelakh. – Reuters