Syrian rights activists say government security forces have resumed their assault on the protest hub of Homs, a day after the Arab League agreed to call for a peacekeeping force and boost support for the opposition to President Bashar al-Assad.

The activists said the shelling Monday targeted the Baba Amr district of Homs. They say hundreds of people have been killed in the central city since the government began bombarding opposition-dominated areas on February 4.

British Foreign Secretary William Hague said Monday the Arab League “could not have sent a clearer message to Syria” when it adopted a resolution calling on member states to provide full support to the Syrian opposition.

Hague said in a statement that Mr. Assad “must be in no doubt” of the international community's determination to bring an end to the violence in Syria.

Arab League foreign ministers also agreed Sunday to press for a United Nations Security Council resolution authorizing an Arab-U.N. peacekeeping force to implement a cease-fire in Syria.

Damascus quickly rejected the resolution. Syrian Ambassador to the Arab League Ahmed Youssef said it reflects the “hysteria” of Arab governments who “failed” to achieve a Security Council resolution authorizing “foreign intervention” in Syria.

Russia and China vetoed a Western- and Arab-backed resolution earlier this month. It would have endorsed an Arab League plan for Mr. Assad to step aside.

Saudi Foreign Minister Prince Saud Al-Faisal urged his Arab League counterparts to take “decisive” action after what he called the failure of previous efforts to stop “massacres” of the Syrian people.

The Arab League resolution adopted Sunday also calls on Syria's disparate opposition groups to unite before a new coalition of nations called the “Friends of Syria” meets in Tunisia on February 24. The United States and its European and Arab allies agreed to form the group in response to Russia and China blocking action by the U.N. Security Council to end the Syrian government's crackdown on the 11-month uprising.

The United Nations said last month that violence linked to the uprising had 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.