Thousands of demonstrators took to the streets in Syria Friday (August 31st) after weekly prayers, AFP reported.

"We will not surrender, despite your tanks and guns!" protesters chanted in the Damascus district of Assali. Security forces reportedly blocked roads leading into the capital.

"How beautiful you are, O freedom!" children chanted at a protest in Aleppo.

Protests were held despite continued fighting between opposition and government forces.

Opposition forces attacked a security service building in west Aleppo at dawn and clashes broke out later in the Sayf al-Dawla, Salaheddine and Hanano districts.

In Idlib province, opposition forces on Friday seized part of the Abu Zohur military airport, where they claim to have shot down a government fighter jet on Thursday, the Syrian Observatory for Human Rights reported.

Meanwhile, the Syrian army campaign against opposition districts in Homs entered its 90th day on Friday, the Observatory reported.

"The army's bombing has been so merciless that even if the siege were broken tomorrow, most people would not be able to return home," Rami Abdel Rahman, the observatory's director, told AFP.

On Friday, UN Secretary-General Ban Ki-moon said he set "demands for all sides to cease all forms of violence" during a meeting with Syrian Prime Minister Wael al-Halqi and Foreign Minister Walid al-Muallem.

At the meeting, held on the side-lines of the two-day Non-Aligned Movement summit, Ban said he placed "primary responsibility" on the Syrian government "to halt its use of heavy weapons".

"What is important at this time is that all the parties must stop the violence. All those actors who may be providing arms to both sides must stop," he said at a news conference after the meeting.

Ban also said he held meetings with Lakhdar Brahimi, the joint UN-Arab League special envoy to Syria, who succeeded Kofi Annan in international efforts to establish peace in Syria.