A human rights group said more than 50 people had been killed across Syria as protests took place on the so-called "Friday of anger", pan-Arab al-Jazeera TV reported.

Thousands of Syrians took to the streets earlier Friday in the cities of Homs, Hama, Qamishli, Banias, and some suburbs of the capital Damascus, calling for lifting the siege on the southern town of Daraa, according to Al-Jazeera.

Syria has been gripped by months of protests that erupted in a number of cities amid calls for sweeping reforms. The government said 293 policemen were wounded by attacks allegedly launched by "extremist terrorist groups".

The Syrian authorities blamed the unrest on "armed thugs and foreign conspiracy."