Security forces opened fire Friday as thousands of anti-government protesters took to Syria's streets in a weekly ritual of defiance and demands for President Bashar Assad's ouster, activists said. They said at least 20 people, including two children, were killed in Damascus and elsewhere.

Four were killed in Barzeh, a Damascus district five kilometres from the city centre, said Syria-based human rights activist Mustafa Osso. He said they were felled by security forces' guns. But Syrian state television said gunmen, otherwise unidentified, had opened fire on security personnel and civilians, killing three civilians and wounding several security force members.

Three other fatalities occurred in al-Kasweh, a suburb of the capital; four in the central city of Homs, and one in Hama, also in central Syria, said the the Local Co-ordination Committees, which track the Syrian protests. Protests in several other provinces also came under fire but it was not immediately clear whether there were casualties, said a spokesman for the group, Omar Idilbi.

The committees said the deaths included a 12-year-old boy, Rateb al-Orabi, killed when security forces fired on protesters in the Shammas neighborhood in Homs, and a 13-year old boy in al-Kasweh. The reports could not be independently verified.

"Our revolution is strong! Assad has lost legitimacy!" protesters chanted in the Damascus suburb of Zabadani, according to video posted on YouTube. Another showed protesters chanting: "Oh Bashar, you coward, pack your bags and go to Iran."

The military crackdown has failed to silence a pro-democracy movement that has now lasted more than 100 days. The Syrian opposition says 1,400 people have been killed in the continuing government crackdown.

In northern Syria, activists said at least 15,000 people held a protest on the highway linking the country's two main cities, Damascus and Aleppo. Thousands marched in Amouda and Qamishli in the northeast and in other provinces, Osso said.

Dissidents reported a strong security presence in many locations. In Homs, all roads leading to the city center were reported blocked.

An eyewitness in Homs said protests took place in every city district Friday. He said hundreds of security personnel had been brought in by bus since early morning and encircled the city's center.

Meanwhile, a prominent Syrian opposition figure, said Saturday some 200 regime critics and intellectuals will meet in Damascus on Monday to discuss strategies for a peaceful transition to democracy.

The one-day gathering will be the first such meeting of Damascus-based regime opponents, many of whom have long been persecuted by the Assad government.

Dissident Louay Hussein said Syrian authorities had not objected to the meeting. It will come one week after President Assad, in a nationally televised speech, spoke of convening his own national dialogue to discuss political reforms.

Protesters deny any foreign influence

In the central city of Hama, activists said a massive protest took place in the city's main Assi square. Online footage showed huge numbers of people gathered, many waving Syrian flags and crying for the regime's downfall. A large purple banner was unfurled over a building, reading: "Long live free Syria, down with Bashar Assad."

The video and other reports from inside Syria could not be independently verified, since the Damascus government has banned all but a few foreign journalists and restricted local media's reporting.

The Syrian regime blames foreign conspirators and thugs for the unrest, but the protesters deny any foreign influence in their movement, during which they say authorities also have detained 10,000 people.

The protests, which have occurred every Friday after weekly Muslim prayers, come as Syrian refugees stream across the border to safe havens in Turkey to escape a military sweep in Syria's northwest. More than 1,500 Syrian refugees crossed into neighboring Turkey on Thursday alone, boosting the number sheltered in Turkey to more than 11,700.

International condemnation on Damascus was mounting steadily. The European Union announced Thursday it was slapping new sanctions on the Syrian regime and U.S. Secretary of State Hillary Rodham Clinton said the movement of Syrian troops right up to the Turkish border could prove dangerous, as concerns of possible confrontations grew.

Turkey sets up 6th camp

Citing residents on the ground, Osso said the military has deployed heavily in areas across the border from Turkey and set up checkpoints. He said the few thousand people who had been on the Syrian side of the border had all fled into Turkey.

"The few who did not were arrested," he said, adding 100 people were arrested in the past two days.

Anticipating an exodus from Syria's second city, Aleppo, Turkish officials were setting up a sixth camp with up to 800 tents near a border crossing.

On Thursday, Syrian soldiers patrolled in military vehicles and on foot around the border village of Khirbet al-Jouz, according to Associated Press journalists who watched their movements from the Turkish side. The Local Co-ordinating Committees said residents reported tanks had entered the village and snipers were spotted on rooftops Thursday.

The Syrian army's operation was the closest Syrian troops had come to Turkey since the military crackdown in the area began two weeks ago.

Turkish Foreign Minister Davutoglu told reporters Friday he had conveyed Turkey's "concerns and thoughts" about the operation near Turkey's border in a telephone conversation with his Syrian counterpart on Thursday.

EU expands sanctions

He said he would continue to talk to Syrian officials to ensure that "reforms and peace are brought about as soon as possible."

"We hope that Syria is successful in renewing itself in a stable manner and comes out of the situation stronger. We will do all that we can to help," he said.

In Brussels, the EU said it had expanded its anti-Syrian sanctions list, targeting seven more individuals and four companies, bringing to 34 the number of people and entities faced with an asset freeze and travel ban, including Assad.

The EU also has an embargo on sales of arms and equipment that can be used to suppress demonstrations.