There were unconfirmed reports of a fresh massacre in Syria on Wednesday as representatives from 55 countries assembled in Washington to explore ways to sharpen the impact of economic sanctions against the Syrian government.

The reports said dozens of civilians in a small village near the central city of Hama were slain by pro-government militias Wednesday afternoon, echoing the circumstances of the killings of more than 100 people in the village of Houla on May 25.

Two activists in Hama said Wednesday that at least 30 people, and possibly many more, had been killed in Qubair, northwest of Hama, after the militias known as the shabiha raided the village. Government forces had blocked roads leading to the village and prevented activists from gathering evidence of the killings, they said.

But one of the activists, Asem Abu Mohammed, said he had received frantic calls for help from people in the village starting in the late afternoon.

Another activist, Mousab al-Hamadi, said people in the village told him that many women and children were among those hacked to death with knives by the militiamen.

Senior Obama administration officials invoked the Houla massacre multiple times Wednesday as they sought to encourage allies to toughen sanctions against Syria. The carnage in Houla represents one of the bloodiest incidents of the 14-month-old uprising against President Bashar al-Assad. More than 10,000 people have died in the conflict, according to estimates by the United Nations.

“We gather in the shadow of a massacre,” Treasury Secretary Timothy F. Geithner told members of the “Friends of Syria” group, convened to look for ways to increase pressure on Assad.

“Nothing we can say can adequately respond to such an event, nor can sanctions alone bring about the change we seek,” he added. “But sanctions can play an important role.”

Geithner and other U.S. officials at the event urged countries to unilaterally impose sanctions on Syria rather than waiting for action from the U.N. Security Council, where Russia and China have blocked consideration of tougher penalties against Assad.

Secretary of State Hillary Rodham Clinton, in a statement delivered to the conference, said the killings at Houla had “exposed the Assad regime’s determination to continue waging war on the Syrian people.”

“The international community cannot sit idly by, and we won’t,” said Clinton, who was traveling Wednesday in Central Asia.

The Obama administration has called for Assad to step down and has imposed a variety of economic sanctions against his government.