At least 11 people were killed Friday when Syrian security forces fired on crowds as thousands of protesters took to the streets nationwide in another round of demonstrations aimed at overthrowing President Bashar Assad.

The demonstrators gathered throughout the north and around the capital, Damascus, despite a heavy military presence and the fear of the continuing military crackdown on the movement protesting against Syria's autocratic regime. Protesters have been under assault by pro-government forces for more than 100 days.

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

Deaths were reported near Damascus and elsewhere.

Details of Friday's violence have not been independently confirmed, largely because Syria does not permit outside media to cover 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 the border into Turkey 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.

Syrian troops are said to be within 500 meters of the border.

Syria's deployment is the closest its troops have come to Turkish territory since military operations 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 says the border scene is “very worrisome,” and she has warned Syria to pull back its troops. She says their presence is worsening an already bad situation for refugees and risks sparking border clashes with the Turks.