Activists say Syrian forces killed at least six people in clashes with protesters Friday as tens of thousands took to the streets nationwide against President Bashar al-Assad.

Protesters gathered Friday near the Turkish border, as well as in central Syria and areas of the capital, Damascus. Rights groups say more than 1,400 people have been killed since mid-March, most of them unarmed protesters.

Details of events in Syria are difficult to independently confirm because the government allows very few foreign news reporters into the country and restricts their movements.

Friday's latest violence comes as U.S. Secretary of State Hillary Clinton says time is running out for the Syrian government.

Clinton made the comments at the “Community of Democracies'' gathering in Lithuania's capital, Vilnius. She said the government must make genuine reforms or face increased resistance.

Clinton also said Mr. Assad's efforts to reach out to the opposition through one meeting earlier this week was not sufficient. She added that allowing an opposition meeting in Damascus while deploying tanks in the north was not sending a coherent message.

Syria has continued a brutal crackdown on anti-government protesters calling for the president to step down. Security forces killed at least 12 people in two days during an ongoing military operation this week near the Turkish border in the country's northwest.

Pro-government forces also appear to have been preventing residents in recent days from crossing into Turkey, where more than 12,000 Syrians have fled to escape the violence in their homeland. Hundreds more Syrian refugees have left for Lebanon.

Turkish officials said only five Syrians made it across the border Thursday, the lowest number in days.