Syrian rights activists say government forces have launched an assault on the central flashpoint city of Hama, while an explosion hit an oil pipeline in the opposition stronghold of Homs.

The activists say government troops stormed residential areas of Hama Wednesday and that telephone lines in the city were cut.

In Homs, about 40 kilometers to the south, activists say the pipeline explosion near the rebel-held Sunni Muslim district of Baba Amr sent a large plume of smoke into the air. They blame the military for the blast, while the government says “terrorists” are responsible.

One of Syria's two refineries is in Homs, and activists say a nearly two-week assault on the city by government forces has killed hundreds of people.

Syrian officials have blamed “armed terrorists” for an 11-month uprising against President Bashar al-Assad's autocratic rule.

Arab diplomats on Tuesday circulated a draft resolution to United Nations General Assembly members calling on Syria to stop its deadly crackdown on the opposition and accusing the government of rights violations.

The diplomats say the resolution is likely to be put to a vote on Thursday and receive broad support in the 193-nation body.

U.N. General Assembly resolutions are non-binding and cannot be vetoed. Russia and China vetoed a U.N. Security Council resolution earlier this month, blocking the body from endorsing a Western- and Arab-backed plan for President Assad to step aside as a way of ending the crisis.

U.S. officials say President Barack Obama expressed disappointment with China's veto at a Tuesday meeting with visiting Chinese Vice President Xi Jinping. At another Washington event attended by Xi, Vice President Joe Biden said the United States “strongly disagreed” with Beijing and Moscow for vetoing a resolution against what Biden called “unconscionable violence” by the Assad government.

China's official Xinhua news agency says Xi told Biden that Beijing's position on Syria is aimed at “safeguarding peace and stability in the Middle East” and is “in line with international principles.” Both China and Russia have said the Security Council must not take sides in a domestic conflict or provide a pretext for foreign military intervention in Syria.

U.N. High Commissioner for Human Rights Navi Pillay said Monday the Security Council's failure to act has “emboldened” Mr. Assad to try to “crush dissent with overwhelming force.”

The United Nations said last month that violence linked to the uprising has killed more than 5,400 people. U.N. officials stopped updating the death toll in January, saying it was too difficult to obtain information. Rights groups say hundreds more people have been killed since then.