"An immediate de-escalation and cessation of violence is imperative," Rosemary DiCarlo, the UN lead for political and peacebuilding affairs, told a Security Council meeting in New York.

Lebanon was drawn into the war last week when Iran-backed Hezbollah attacked Israel in response to the killing of Iranian supreme leader Ayatollah Ali Khamenei in US-Israeli strikes.

Around 30 countries, including those with UN peacekeepers in Lebanon, earlier Wednesday issued a joint statement voicing "deep alarm at the escalation of hostilities."

"Faced with war, Lebanon must be supported. Its sovereignty and territorial integrity must be preserved," Jerome Bonnafont, the French ambassador to the United Nations, told reporters before the Security Council meeting.

He added that the countries he represented, including France, Britain, Germany, India and Korea, "condemn in the strongest terms" Hezbollah's attacks.

Israel's UN envoy Danny Danon said that Israeli forces will continue to operate in Lebanon "as long (as) there will be a threat against us."

"Israel does not want to be operating, but Israel will not accept rockets fired at our people, and we will do whatever is necessary to stop them," Danon told reporters.

- 'Grave peril' -

During the Security Council meeting, several states including France and Britain condemned the Hezbollah attacks -- saying they had dragged Lebanon into regional war.

Meanwhile, Russia primarily blamed the United States and Israel over their strikes on Iran.

"It is the American and Israeli military escapade that is plunging the overall region ever deeper into chaos," said Anna Evstigneeva, Russia's deputy UN envoy.

The Lebanese ambassador, Ahmad Arafa, said his country "finds itself trapped in a war that it did not choose between Israel and Hezbollah."

"Lebanon is facing an extremely dangerous moment and a true humanitarian catastrophe," he said.

The death toll from 10 days of fighting reached 634 on Wednesday, with more than 800,000 people displaced, according to Lebanese officials.

UN aid chief Tom Fletcher warned the Security Council of "a moment of grave peril for Lebanon and for the region."

"As a result of the region's latest war, and following months of violence, we've watched the humanitarian crisis in Lebanon intensify with alarming speed," he later added.