Hamas confirmed that its militants have fired Grads (military-grade rockets) from northern Gaza Strip yesterday morning in response to the killing of five of its militants.

The two Soviet-made Grads landed near a factory and a parking lot in the Israeli coastal city of Ashkelon respectively, causing damage to several cars, according to Israeli sources.

In the meantime, tens of rockets launched by armed Palestinian groups, mainly Hamas and the less influential Islamic Jihad, have been landing in Israeli border towns.

Late Tuesday, Israel killed three Hamas militants after spotting them planting explosives near the security fence that separates Israel and northern Gaza Strip.

Israeli radio reported that 60 rockets and mortar shells have hit Israel since Wednesday morning, adding that two residents were treated for shock.

Meanwhile, a Palestinian civilian was seriously injured when an Israeli missile hit the front of his house in northern Gaza city, witnesses and medical sources.

Emad al-Drimley, a Gaza journalist, said his family were waken up at 4 am local time (0200 GMT) by the sound of a big blast that hit their house. "My brother Eyad, 37, was seriously wounded by shrapnel," Emad said.

Neighbors of Emad said the Israeli missile hit his house moments after militants fired rockets into Israel from nearby.

The latest violence is the bloodiest since a six-month ceasefire between Hamas, which controls Gaza Strip, and Israel expired.

Israel and the Palestinian militants have violated the Egypt-brokered ceasefire since early November, with Israel launching military operations into Gaza, triggering Palestinian rocket attacks in response.

Israel also restored tight restrictions on Gaza commercial crossings in a bid to deter the Palestinian rocket fire.

Palestinian officials said Israel will not open Kerem Shalom and Karni crossings yesterday to allow aid convoys into Gaza. Israeli Defense Minister Ehud Barak ordered the crossings to remain close in response to the rockets.