Anti-Syrian regime protesters, shout slogans as one of them holds an Arabic placard reading: "News alert, Bashar Assad to the hell," during a demonstration in Tripoli.

Syrian security forces fired on thousands of protesters Friday, killing a teenage boy and at least 15 other civilians as accounts emerged of more indiscriminate killing and summary executions by the autocratic regime of President Bashar Assad, activists said.

The three-month uprising has proved stunningly resilient despite a relentless crackdown by the military, the pervasive security forces and pro-regime gunmen. Human rights activists say more than 1400 Syrians have been killed and 10,000 detained as Assad desperately tries to maintain his grip on power.

"What is our guilt? We just demanded freedom and democracy nothing else," said Mohamed, 27, who spoke from a refugee camp in neighbouring Turkey where nearly 10,000 Syrians have fled.

Mohamed, who asked to be identified only by his first name for fear of reprisals, and other refugees offered harrowing accounts of the regime's bombardment.

"I saw people who were beheaded with machine-gun fire from helicopters," and a man tortured to death when security forces poured acid on his body, he said.

He said a sugar factory in Jisr al-Shughour was turned into a jail where they "hold quick trials and execute anyone who they believe participated in protests". Jisr al-Shughour was a town that was spinning out of government control before the military recaptured it last Sunday.

UN envoy Angelina Jolie travelled to Turkey's border with Syria on Friday to meet some of the refugees, and she was greeted by a 45-foot-long (15-metre) banner that read: "Goodness Angel of the World, Welcome," in English and Turkish. Police prevented media coverage of the visit.

Assad is expected to give a speech as early as Sunday in what would be only his third public appearance since the uprising began in mid-March, inspired by the revolutions sweeping the Arab world.

The uprising has proven to be the boldest challenge to the Assad family's 40-year dynasty in Syria. Assad, now 45, inherited power in 2000, raising hopes that the lanky, soft-spoken young leader might transform his late father's stagnant and brutal dictatorship into a modern state.

But over the past 11 years, hopes dimmed that Assad was a reformist at heart. Now, as his regime escalates a brutal crackdown, it seems increasingly unlikely that he will regain any political legitimacy.

On Friday, a French official said the European Union was preparing new, expanded sanctions that would target "economic entities" in Syria.

France, Britain, Germany and Portugal are also sponsoring a draft resolution at the UN Security Council to condemn Syria. They say they have the votes needed to pass it but want more support.

Syria's foreign minister, Walid al-Moualem, told the Security Council in a letter circulated Friday that the proposed resolution is based on erroneous information and would intrude in Syria's internal affairs.

The resolution, he added, would help the "extremists and terrorists" he blamed for the country's violence.

Despite widespread calls for an end to the crackdown, the country's future is far from certain - particularly as there is no clear alternative to Assad.

Syria has a pivotal role in nearly every thorny Mideast issue. A staunch Iranian ally, Syria backs the militant groups Hezbollah in Lebanon and Hamas in the Gaza Strip. It has also provided a home for some radical Palestinian groups and has exerted influence in neighbouring Iraq.

Chaos in Syria, as a result, has wide implications on the region.

Syria has tried to exploit those fears, alleging that armed gangs and foreign conspirators are behind the unrest, not true reform-seekers. In what has become a weekly back-and-forth between activists and the government, both sides offered divergent death tolls.

Syria's state-run TV said Friday that a policeman was killed and more than 20 were wounded when "armed groups" opened fire at them. It added that six police officers were wounded in Deir el-Zour when gunmen attacked a police station in the area.

But the Local Coordination Committees, a group that documents the protests, and Syria-based rights activist Mustafa Osso said that 16 people were killed, all of them civilians, citing witnesses on the ground.

Nine people were killed in the central city of Homs, two in the eastern town of Deir el-Zour and two in the Damascus suburb of Harasta, one in the major northern city of Aleppo. A boy believed to be 16 years old, who was in the streets protesting, and another person died in the southern village of Dael, the Local Co-ordination Committees said.

It's impossible to independently confirm many accounts coming out of Syria. Foreign journalists have been expelled from the country and local reporters face tight controls.

Protests were reported across the country Friday, with tens of thousands pouring into the streets of the central cities of Homs and Hama, the southern villages of Dael and Otman, coastal cities of Latakia and Banias, the Damascus suburbs of Qudsaya and Douma as well as the capital, Damascus.

In the northeast, thousands marched in Amouda and Qamishli, chanting for the regime's downfall, the Local Co-ordination Committees said. In the southern village of Dael, activists said cracks of gunfire could be heard at the center where a protest was held.

Also Friday, the Syrian unrest appeared to be spilling into neighbouring Lebanon.

A senior member of a Lebanese political party allied with Syria, along with two other civilians and an off-duty soldier were killed after gunmen opened fire and lobbed a grenade near hundreds of people holding an anti-Assad protest, a security official said in Beirut. At least 10 people were wounded.

The conflict also has exposed sectarian tensions that have long bedevilled this volatile region.

The Assad regime is dominated by the Alawite minority, an offshoot of Shiite Islam, but the country is overwhelmingly Sunni Muslim.

Alawite dominance has bred resentment, which Assad has worked to tamp down by pushing a strictly secular identity in Syria. But the president now appears to be relying heavily on his Alawite power base to crush the resistance, beginning with highly placed Assad relatives.