A sharp rise in the number of deaths in the Syrian uprising is testing a ceasefire deal and casting fresh doubt on the success of a United Nations peace plan.
Activists say nearly 70 people were killed on Monday, most in a government crack-down in the city of Hama.
The UN is pressing to increase its monitors from a handful to 300 and special envoy Kofi Annan is due to brief the Security Council on Tuesday.
Although the overall level of violence has dropped since a UN-brokered ceasefire came into effect on 12 April, the Syrian government has been accused of failing to abide by key terms of the truce plan, including pulling all forces from urban areas and allowing peaceful demonstrations.
The continuing bloodshed on Monday sparked growing criticism from opposition activists of the fledgling UN mission, which still numbers just eight observers out of a planned initial deployment of 30, AFP reports.
Despite concerns over the mounting violence that the UN says has left over 9000 people dead in 13 months of fighting, UN Secretary-General Ban Ki-moon gave the go-ahead for the deployment of 300 ceasefire monitors to Syria from next week.
Mr Ban insisted on Monday that the government of President Bashar al-Assad ensure the protection of the unarmed observers and allow them to travel freely throughout the country.
Government troops strafed the Arbaeen neighbourhood of the central city of Hama and its environs on Monday with light and heavy machine guns, the Syrian Observatory for Human Rights said. Video footage posted online by activists showed mortar rounds hitting the area, with plumes of smoke rising to the sky.
UN observers visited several rebel suburbs near the capital and were met by thousands of protesters demanding the collapse of the Assad regime. Monitors also visited the town of Zabadani, where regime forces and rebel fighters have clashed repeatedly in past months.
Activists' videos showed monitors passing by army tanks posted in the streets, despite a call within UN-Arab League envoy Kofi Annan's six-point peace plan for the withdrawal of armour from residential areas.
However, Deputy Foreign Minister Faisal Meqdad stressed his government's "total commitment to respecting the Annan plan," adding that the "armed terrorist groups" - a reference to the rebels - had not yet accepted it.
Arab League chief Nabil al-Arabi has called for a political process to resolve the crisis.
In a sign of Western frustration with Damascus, the European Union agreed to impose new sanctions on the regime, banning luxury goods exports and further restricting the sale of items used to repress dissidents.
Brussels also expanded the blacklist of dual-use goods that can be used to crack down on the population or manufacture equipment used for internal repression.
United States President Barack Obama announced new sanctions intended to prevent the authorities in Iran and Syria using sophisticated communications equipment against dissidents.
Mr Obama announced the measures against "digital guns for hire" in a speech at the US Holocaust Museum. He said the two countries were conducting violent campaigns against their own people, assisted by what he called the malign use of technology.
The executive order signed by Mr Obama on Sunday freezes US assets linked to those helping satellite, computer and phone network monitoring in Syria as well as Iran.
The specific targets include Syria's General Intelligence Directorate, Iran's Ministry of Intelligence and Security and its Revolutionary Guard Corps.
The order also specifices Syrian cellphone company Syriatel and the Iranian internet provider Datak Telecom, as well as a number of individuals. It says GPS, satellite communications, mobile phone and internet technology employed by democracy activists across the Middle East and North Africa is being used against them.