Thousands of protesters took to the streets across Syria Friday as a series of demonstrations continue aimed at overthrowing President Bashar Assad's autocratic rule.

The demonstrators gathered throughout the north and around the capital, Damascus, despite a heavy military presence and the fear of a continued government crackdown against the anti-government movement that has lasted more than 100 days.

There are reports of security forces firing on protesters.

An activist with the London-based Syrian Observatory for Human Rights told the French news agency by phone Friday from the town of Kiswah that security forces had opened fire on demonstrators, injuring an unknown number of people.

The report of violence has not been independently confirmed and Syria does not allow outside media coverage of protests. Activists say Syria's crackdown has killed at least 1,400 people in the last three months.

Turkish officials said Friday that more than 1,500 Syrian refugees crossed its border on Thursday after Syrian troops stormed the town of Khirbet al-Jouz.

According to Turkish government estimates, nearly 12,000 Syrians are now housed in massive tent encampments in Turkey even as the Syrian troops have moved within 500 meters of the border.

Syria's deployment is the closest its troops have come to neighboring Turkey since the military operation in the area began two weeks ago. Turkish troops moved their border positions several hundred meters back, apparently to avoid potential confrontations with Syrian units.

U.S. Secretary of State Hillary Clinton called the border scene “very worrisome” and warned Syria to pull back its troops. She said their presence is worsening an already bad situation for refugees and risks sparking border clashes with the Turks.