Britain has called for stronger international pressure on Syria, as residents and rights activists said Syrian security forces attacked the central city of Hama for a second day.

The activists said Syrian tanks shelled Hama Monday, a day after killing at least 80 people in the city.

British Foreign Secretary William Hague said Monday there should be stronger sanctions against the government of Syrian President Bashar al-Assad, but the British diplomat said international military intervention is “not a remote possibility.”

Hague said Arab countries, including Turkey, have to be among those pressuring Syria.

The United States and European Union have condemned violence by Syrian security forces against civilians.

Russia on Monday said it was concerned about reports of large numbers of casualties, and called for an end to violence against both civilians and representatives of the government.

U.S. President Barack Obama said Sunday he is “appalled” by Syria's use of violence against its own people, and that the “horrifying” reports demonstrate the “true character” of Syrian President Bashar al-Assad's government.

It is hard to verify accounts of the unrest in Syria because the government has barred most foreign media from reporting and traveling freely in the country. Some estimates say as many as 140 died in the clashes Sunday as Syrian soldiers backed by tanks fired on citizens.

Italy and Germany have called for an urgent meeting of the United Nations Security Council to review the situation in Syria.

U.N. Secretary-General Ban Ki-moon urged the Syrian government to halt the use of force against its citizens immediately and respect their human rights.

Former Lebanese prime minister Saad Hariri also criticized Sunday's attack, and said “silence on the international and Arab levels” about the situation in Syria is leading to the loss of more Syrian lives.

Citizens have held large protests against Mr. Assad in Hama, an important city in the history of Syrian resistance. In 1982, the current president's father, President Hafez al-Assad, used military force to quell a rebellion there, killing thousands of people.

In the country's south early Sunday, residents say security forces killed three people and wounded several others as they stormed the village of al-Hirak. They say forces also arrested more than 100 people in the raid.

Activists say President Assad is trying to crush the largely peaceful uprisings against his government that broke out across much of the country in March.

Rights groups say Syrian forces have killed at least 1,600 civilians during the government's crackdown. The government has blamed much of the violence on terrorists and militants who it says have killed hundreds of security personnel.