UN Secretary-General Ban Ki-moon said on Friday reports of a massacre by Syrian government forces cast "serious doubts" on Syrian President Bashar Assad's commitment to a UN-backed peace plan while the United States expressed outrage at a massacre.
"I condemn, in the strongest possible terms, the indiscriminate use of heavy artillery and shelling of populated areas, including by firing from helicopters," Ban said in a statement.
"They also cast serious doubts on President Assad's recent expression of commitment to the six-point plan in his meeting with the Joint Special Envoy," he said, referring to Assad's meeting with international envoy Kofi Annan in Damascus on Monday.
Earlier Friday, US Secretary of State Hillary Clinton expressed outrage over reports of the Syrian government assault in the rebellious Hama region and urged the UN Security Council to make clear to Damascus that there would be consequences.
Accounts of the attack on the village of Taramseh, including the use of artillery, tanks and helicopters, provide "indisputable evidence that the regime deliberately murdered innocent civilians," she said.
"We call for an immediate ceasefire in and around Hama to allow the UN observer mission to enter Taramseh," Clinton, who is traveling in Asia, said in a statement issued in Washington.
"Those who committed these atrocities will be identified and held accountable."
Syrian opposition activists have put the death toll at Taramseh at anywhere from 100 to more than 200 people and said it was the work of government troops and militia allies.
There has been no independent account of the battle, which the government described as a massacre by "terrorist groups."
Clinton said the massacre underscored the need for major powers to increase pressure on Assad's government to allow for a UN-backed political transition plan to move forward.
She said the UN Security Council - where veto-holders Russia and China have thrown the brakes on western efforts to pass more punitive measures against Damascus - should now make clear that there would be consequences for non-compliance.
"History will judge this Council. Its members must ask themselves whether continuing to allow the Assad regime to commit unspeakable violence against its own people is the legacy they want to leave," Clinton said.
Clinton's comments came as the Security Council faces deep divisions over Western demands that a new resolution on Syria now under debate should authorize actions ranging from sanctions to military intervention if the violence does not stop.
Russia, which remains Assad's chief international ally, has said it opposes such moves. The council is due to vote on July 18.
The White House said on Friday that reports of the Taramseh massacre had eliminated any doubt over the need for a coordinated international response.
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"Through these repeated efforts, through these repeated acts of violence against the Syrian people, President Assad has lost legitimacy to lead. It is time for him to go," White House spokesman Josh Earnest said.
"We are hopeful that we'll see continued unity on the international scale to press Assad to leave power."