"We attacked seven tunnels near the [southern Gaza town of] Rafah. There were secondary explosions, showing they contained weapons material," the spokesperson said.

"It was a response to two Qassam rocket attacks today and continued rocket fire."

Supply routes

Makeshift tunnels are used by Palestinians to supply the Gaza Strip, which is undergoing an Israeli blockade, with essential supplies.

Israel says that the tunnels are also used to smuggle weapons to Palestinian factions.

One of Israel's stated goals of their 22-day offensive on the Gaza Strip, which began on December 27, was to shut down the smuggling tunnels.

About 1,300 Palestinians and 13 Israelis were killed during the offensive.

About a dozen Palestinian factions are to continue talks in Cairo, the Egyptian capital, on Thursday in an attempt to bring about unity in the face of Israeli occupation.

Unity dialogue

Fatah and Hamas, the two main factions, said on Wednesday that they would exchange prisoners in Gaza and the West Bank, as a goodwill gesture ahead of the talks to establish a unity government.

A Palestinian official said that about 40 Hamas prisoners in the West Bank had already been released by Fatah, with more to follow.

Fatah and Hamas disagree on how to deal with Israel. Hamas is willing to accept an 18-month truce, but reserves the right to fight its neighbour, whereas Fatah renounces violence in favour of negotiations.

A rift has further widened between the two sides since Hamas forcibly took control of the Gaza Strip in June 2007, after which Israel tightened its blockade of the Gaza Strip.

Egypt is also continuing to try to broker a ceasefire between Israel and Hamas following Israel's offensive.