Syrian security forces shot at least 16 civilians dead in Syria's third largest city of Homs, the Al Arabiya TV channel reported.
Homs, the capital of an eponymous western province, is one of the hotspots of the ongoing protests against the rule of President Bashar Assad. This is not the first time troops loyal to the president were deployed in the city.
The security forces "fired indiscriminately" on residents of the Baba Amro neighborhood, one of the activists said by telephone to AFP.
Syrian tanks also stormed two northwestern towns near the border with Turkey in an attempt to crush dissent, Al Jazeera said. The violence came a day after Turkish Prime Minister Recep Tayyip Erdogan demanded Assad to "stop all kinds of violence and bloodshed."
"The Syrian Observatory for Human Rights (SOHR) said at least one woman was killed and 13 people injured on Wednesday when 12 tanks and armoured vehicles, entered the towns of Taftanaz and Sermin, around 30km from the border with Turkey," Al Jazeera said on its website.
More than 1,600 civilians are thought to have been killed and 3,000 missing since protests began in the southern city of Deraa in mid-March. According to government data, 340 servicemen and security officers were also killed.