The Israeli air force is under orders to blast ten buildings in south Beirut, a Hezbollah stronghold, for every rocket the Shiite militant group fires at the Israeli port of Haifa, army radio said on Monday.

"Army chief of staff Dan Halutz has given the order to the air force to destroy ten multi-storey buildings in the Dahaya district (of Beirut) in response to every rocket fired on Haifa," a senior air force officer told the station.

Hezbollah rockets fired from southern Lebanon killed two people on Sunday in the northern city of Haifa, which has been hit by dozens of missiles since the latest conflict started on July 12.

Israel kept up its offensive on Lebanon on Monday, with its ground forces pushing deeper into the territory and warplanes carrying out a new blitz of about 40 air raids overnight.

UN humanitarian coordinator Jan Egeland on Sunday accused Israel of violating humanitarian law as he toured bombed-out areas of south Beirut.

"This is destruction of block after block of mainly residential areas. I would say it seems to be an excessive use of force in an area with so many citizens," he said.

AFP