There has been widespread condemnation of an Israeli attack that killed 18 people, including 13 members of one family, in northern Gaza.
Syria said the international community and United Nations Security Council had a duty to stop what it called such massacres and hold Israel accountable.
The Palestinian Prime Minister, Ismail Haniyeh, has called for a suspension of talks on a new government following the attack. He also called for an immediate session of the UN.
Italy's Foreign Minister Massimo D'Alema described the shelling in Beit Hanoun as 'unacceptable' and called for an urgent international initiative to stop the violence.
Reports said seven children and four women were among those killed when tank shells struck seven houses overnight.
The Israeli army claimed it had fired artillery shells in response to militant rocket fire.
Israel had withdrawn from the northern town yesterday following a week-long assault that left 52 Palestinians and one Israeli dead.
Meanwhile, in the occupied West Bank, Israeli soldiers killed four Palestinian militants and a civilian during an early morning raid near Jenin.
President Mahmoud Abbas called the shelling a 'horrible and ugly massacre'.
Talks suspended
Mr Haniyeh has said that talks between his ruling Hamas party and Mr Abbas's Fatah movement on forming a national unity government had been 'suspended' after the incident.
At the opening of an emergency cabinet meeting, the Prime Minister called on the Palestinian people to unite following what he said was 'a barbaric attack' in northern Gaza.
Mr Abbas had been in Gaza since Monday in a bid to form a unity government after months of deadlock and failure to persuade Hamas to soften its hardline stance.
The Islamist movement has refused to recognise Israel, renounce violence and abide by past peace deals.
