Syria unrest: Renewed clashes 'leave 28 dead'
At least 28 people have been killed in fresh clashes in Syria between security forces and protesters, activists say.
They say tanks and helicopter gunships opened fire on crowds in the northern town of Maarat al-Numan, leaving several protesters dead.
The violence came as government forces moved on the nearby town of Jisr al-Shughour where the government said 120 security personnel had been killed.
Hundreds of civilians have fled north into Turkey to escape the assault.
The White House toughened its stance on Syria late on Friday, demanding an "immediate end to brutality and violence" and warning President Bashar al-Assad was leading his nation on a "dangerous path".
Opposition activists earlier told the BBC that the army was adopting a "scorched earth policy" around the town of Jisr al-Shughour.
Helicopter gunships and tanks were said to be firing into the town as advancing troops bulldozed homes and torched crops and fields.
The Syrian government has not commented on the claim.
Anti-government activists said about 15 people died in the northern province of Idlib, most of them in Maarat al-Numan where tanks and helicopters fired on protesters.
Correspondents say it is the first reported use of air power to quell protests in Syria's three-month uprising.
Syrian state TV reported that armed gangs had attacked police stations in the town.
A Syrian opposition figure told the Associated Press news agency by telephone that thousands of protesters had overwhelmed security officers and set light to a courthouse and a police station in the town.
Syria has prevented foreign journalists from entering the country, making it difficult to verify reports from there.
Another five anti-government protesters were killed in the coastal city of Latakia, according to activist sources.
Elsewhere in Syria, two people were reported killed by security forces in Busra al-Harir, southern Deraa province, and another four in the Qaboun district of the capital, Damascus.
Since March, mass protests against the rule of President Assad have become a regular event following Friday prayers.
Human rights groups say more than 1,300 people have died as the government tries to suppress dissent, most of them unarmed civilians. The government rejects the figures and says about 500 security forces have died.
With the unrest showing no sign of abating, the International Committee of the Red Cross (ICRC) called for immediate access to those affected by the violence and those arrested or detained.
The town of Jisr al-Shughour was said to be all but deserted as troops moved in on Friday. Witnesses reported explosions coming from near the town.
The crackdown had been long expected. The Syrian government blamed armed groups for the deaths of 120 security personnel in the town earlier in the week, although there were reports of a mutiny among security forces.
Syrian state TV said armed gangs had prepared defences and set fire to crops and trees around Jisr al-Shughour in order to slow the army's advance.
State TV has been broadcasting images of what it says are soldiers and police shot dead in the town.
The government says local residents requested the army's intervention to restore peace and quiet.
Turkey - which shares a long border with northern Syria - says more than 2,000 Syrians have crossed over, seeking refuge from the expected retaliation on Jisr al-Shughour. The city has a population of about 50,000. It is not clear how many other residents have fled to other locations within Syria.
Turkish PM Recep Tayyip Erdogan has previously been reluctant to criticise Syria, but in an interview quoted by Anatolia news agency, he said the Assad regime was committing "atrocities" against anti-government demonstrators.
"They are not acting in a humane manner. This is savagery," he said in a TV interview on Thursday.