An Israeli air raid killed more than 40 people in a Lebanese village on Monday, Lebanon's prime minister said, and other air strikes killed 19 after diplomatic efforts to end the 27-day-old war stalled.
"An hour ago, a horrific massacre took place in Houla village as a result of the intentional Israeli bombardment that resulted in more than 40 martyrs," Prime Minister Fouad Siniora told an emergency Arab foreign ministers meeting in Beirut.
Residents of Houla said they feared up to 60 people, including many children, had been killed.
They said most of the people were shepherds who had refused to flee the fighting.
Nineteen people were killed in separate strikes on other villages in the south and the eastern Bekaa valley.
Speaking before news of the Houla raid, Lebanese Health Minister Mohammad Khalifeh said the war had killed 925 people, mostly civilians, with 75 missing, presumed dead.
About one-third of the dead were children under the age of 13, he said. Ninety-four Israelis have also been killed.
Hezbollah guerrillas fired more rockets into northern Israel, wounding one person, a day after rockets killed 15 Israelis in the deadliest day of the war for the Jewish state.
Israeli aircraft hit the last coastal crossing on the Litani river between Sidon and Tyre, cutting the main artery for aid supplies to civilians in the south, security sources said.
One international aid group said Israel was providing no security guarantees, effectively paralysing its delivery of aid south of the Litani.
About 22,000 people remain in the region, less than one fifth of the pre-war population, UN figures say.
"Our last remaining supply route into Tyre into the south has been cut," said Christopher Stokes, operations director for the relief group Medecins Sans Frontieres.
"The Israelis have said they cannot provide a security guarantee that our convoy will not be attacked, so if we move, it will be at our own risk and peril," Stokes said.
Hezbollah says it will fight on until Israel stops bombing Lebanon and pulls out its forces. Israel is pressing ahead with its offensive while world powers struggle to agree a UN resolution to end the fighting.
Opposition from Lebanon caused the United States and France to delay a vote on a UN resolution.
They may submit a revised text after Security Council consultations later in the day.
Lebanon's government has demanded that the US-French draft UN resolution include a call for an immediate withdrawal of some 10,000 Israeli troops from its soil.
China and Russia argued the text should take more account of Lebanon's concerns.
That prevented Paris and Washington putting the draft into final form, which could have cleared the way for a Security Council vote on the resolution on Monday.
Some pro-Western Arab governments, such as Saudi Arabia, Egypt and Jordan, initially criticised Hezbollah for provoking the conflict by snatching two Israeli soldiers on July 12.