At least 14 Syrians were shot dead as protesters took the streets following Friday prayers and ahead of a general strike called for Sunday, according to a network of anti-government activists reporting events to a website based in England.

In Homs, the hub of the revolt against President Bashar Assad, they chanted "Syria wants freedom" and "Bashar is an enemy of humanity", Qatar based Al Jazeera television said.

Turkish Foreign Minister Ahmet Davutoglu did not say what action Ankara might take, but he made clear Turkey would not hesitate to insulate the region's security from tumult in Syria. Turkey shares a 900 km border with Syria.

"Turkey has no desire to interfere in anyone's internal affairs. But if a risk to regional security arises, then we do not have the luxury of standing by and looking on," Davutoglu told reporters in Ankara.

"If a government that is fighting its own people and creating refugees, is putting not only their own security at risk but also that of Turkey, then we have a responsibility and the authority to say to them: 'Enough!'" he said.

Peaceful demonstrations calling for reform began in Syria in March, inspired by the Arab Spring, but were met almost from the outset by lethal force.

About 4,600 Syrians have been killed in nine months of protest and violent state suppression, according to Syrian activists. Hundreds have fled over the border to Turkey which has established refugee camps.

Turkey's customs and trade minister earlier said the Cabinet was expected to approve the suspension of a free trade agreement with Syria in retaliation for a similar move by Damascus. Hayati Yazici said Syria had unilaterally suspended the 2008 agreement, which wiped out taxes on most goods. Authorities said the suspension of the deal will lead to taxes of up to 30 percent on some goods.

Four children were among 14 people killed when security forces and pro-regime militias opened fire in several cities across the country after the weekly Friday prayers, the Syrian Observatory for Human Rights reported. Nine of the deaths occurred in Homs, the UK-based Observatory said.

The opposition Syrian National Council earlier warned of the dangers of a "massacre" in the protest hub of Homs, a city in central Syria that it said was circled by government forces.