The United Nations General Assembly is meeting on a Saudi-drafted resolution on Syria, as activists report more violence in the 17-month uprising against President Bashar al-Assad.

Kicking off debate on the resolution late Friday morning, U.N. leader Ban Ki-moon said the Syria conflict is now a “proxy war” and urged major powers to end the violence. He added: “the immediate interests of the Syrian people must be paramount over any larger rivalries of influence.”

Syria allies Russia and China have previously vetoed three resolutions on Syria. Mr. Ban said the Security Council had become “paralyzed” over Syria.

The non-binding U.N. resolution would condemn both the Assad government's use of heavy weapons in the fight against rebel forces and the U.N. Security Council's failure to agree on measures to stop the violence.

The debate comes just one day after Kofi Annan announced his resignation as U.N. – Arab League envoy to Syria, blaming what he called a lack of unity in the Security Council.

Meanwhile, the Britain-based Syrian Observatory for Human Rights said Friday that shelling of a Palestinian refugee camp in the capital, Damascus, Thursday killed at least 21 people. The Observatory did not say who fired the mortars.

Syrian troops were reportedly massing troops and tanks in a Damascus suburb.

The group also reported clashes and government attacks Friday in other areas of the country, including the provinces of Hama, Idlib and Aleppo. In Daraa province, it said government forces were using helicopters.

In the wake of Mr. Annan's resignation, Britain pledged to increase its support for the Syrian rebels.

British Foreign Secretary William Hague told BBC radio Friday that Britain will increase its practical but non-lethal support in the coming weeks “given the scale of death and suffering and the failure so far of the diplomatic process.”

The White House said Mr. Annan's resignation highlights the failure of Russia and China to back meaningful resolutions against Mr. Assad.

Chinese foreign ministry spokesman Hong Lei said China regrets Mr. Annan's resignation and supports the U.N. continuing to play an important role in an appropriate solution to the conflict.

Both the Syrian rebels and the government failed to commit themselves to Mr. Annan's peace plan for Syria, which included an immediate cease-fire and talks on a transitional government. The three Security Council resolutions that China and Russia vetoed would have held President Assad responsible for his failure to abide by the Annan plan and threatened him with sanctions.