The Arab League called on the United Nations on Sunday to impose a no-fly zone over Gaza and lift an Israeli siege of the territory after a flare-up of violence that is stoking fears of a wider escalation.

The death toll since Israel launched retaliation for an attack on a school bus that critically wounded a teenager on Thursday has climbed to 19 Palestinian militants and civilians.

Condemning what it called Israel's "brutal" aggression in Gaza, a gathering of the Arab League's permanent delegates chaired by Oman called on the U.N. to convene its Security Council.

The meeting would "consider the Israeli aggression in the Gaza Strip on an urgent basis to stop its siege and impose a no-fly rule on the Israeli military to protect civilians in the Gaza Strip," the Arab League said in a statement.

An Israeli government official in Jerusalem who declined to be named dismissed the call and said the Arab League should first ensure Gaza militants halt attacks on Israel.

"If the Arab League wants a no-fly zone in Gaza is it also talking about ground-to-ground missiles that are fired from Gaza on Israeli cities? About missiles fired at school buses? About mortar shells fired at farms?" the official said.

"If the Arab League wants Israeli military aircraft to stop flying over the Gaza Strip then it should first ensure there is no reason for them to be there to protect Israeli citizens."

The Cairo-based regional body also said Sudan should press a complaint against Israel at the Security Council over what Sudan has called a missile attack that killed two people.

Israel has declined to comment on Khartoum's accusation it launched the strike near Port Sudan airport on Tuesday night.

"The council of Arab League calls on the Sudanese Ministry of Foreign Affairs and the apparatus of African Union ... to present a complaint against Israel in front of the Security Council and the U.N.'s general assembly," the League said.