Energized by an overwhelming vote of support at the United Nations General Assembly, backers of an Arab League peace plan for Syria said Friday that they were seeking new ways to aid opponents of President Bashar al-Assad and to ensure that an international conference in Tunisia next week puts additional pressure on him to give up power.

The diplomatic momentum, seen in high-level meetings in Washington and Paris, came as thousands of anti-Assad Syrians, perhaps also emboldened by news of the General Assembly vote on Thursday, were reported to have demonstrated in the cities of Dara’a, Aleppo, Idlib, Hama and the suburbs of Damascus after Friday Prayer.

The Local Coordination Committees, an activist group in Syria, reported that pro-Assad forces in those cities as well as the embattled central city of Homs fired on some demonstrators and killed at least 56 people around the country, including 12 deserters from the military. The Syrian Observatory for Human Rights, another activist group, said 26 people had been killed.

The information from the groups could not be corroborated because of the government’s restriction on outside information-gathering in the increasingly violent conflict, which has taken on the trappings of a civil war with a fractious and disorganized opposition.