GAZA/JERUSALEM — Israel launched more air strikes on Gaza on Tuesday as Palestinians kept up rocket fire on Israeli territory, in the worst surge of violence since a 2014 war.

The fighting — that has killed six Palestinians since Monday — threatened to derail efforts by the United Nations to broker a long-term truce and head off another major conflict in the impoverished enclave.

Hamas and other armed factions launched more than 400 rockets or mortar bombs across the border after carrying out a surprise guided-missile attack on Monday on a bus that wounded an Israeli soldier, the military said.

The salvos were the fiercest since the 2014 Gaza war between Israel and Gaza fighters. Hamas said it was retaliating for a botched Israeli commando raid in Gaza that killed one of its commanders and six other gunmen on Sunday. An Israeli colonel was also killed in that incident.

Israel responded with dozens of air strikes against Gaza, hitting buildings overnight. In Gaza, schools, government office and banks were closed on Tuesday. Classes were also canceled in Israeli towns near the border.

Prime Minister Benjamin Netanyahu convened his security cabinet to discuss Israel’s next moves and the military said it had sent infantry and armored reinforcements to the Gaza frontier.

A Palestinian official said Egypt and the United Nations had stepped up efforts with Palestinian factions and Israel to end the current round of fighting “and prevent further escalation”.

In Gaza, Israeli missiles completely flattened four multi-floor buildings, including the TV station, and three other homes. — Reuters