At least five Palestinians have died in an unexplained blast in southern Gaza City, witnesses and hospital officials say.

Representatives of the militant group Hamas said the dead were Hamas activists.

I heard the sound of screaming women Palestinian neighbour

Several other people were injured in the explosion, which came a day after Hamas militants blew up an Israeli tank in the north of the Gaza Strip, killing its crew of four.

In the West Bank, two other Palestinians died in clashes with the Israeli army on Sunday as it arrested a senior member of the Palestine Liberation Organisation in the town of Nablus.

No reason was given for the arrest.

Militant's house

The Gaza blast occurred on Sunday afternoon local time near the home of a Hamas activist in the al-Zeitun area, known as a Hamas stronghold.

"I heard the sound of screaming women, and cars evacuating people from the house. I saw at least three people covered in blood being taken away," a neighbour said.

Reuters news agency said a car laden with explosives had blown up on a farm, but there is no confirmation.

The Israeli army refused to comment on the blast, fuelling speculation that it could have been part of its expected response following the tank attack on Saturday.

However according to the Associated Press news agency, Hamas prevented journalists from inspecting the site.

Correspondents point out that there have been several cases in the past where Palestinian militants have accidentally blown themselves up while manufacturing bombs.

Following the attack on the tank, Israeli Defence Minister Shaul Mofaz told a weekly cabinet meeting his troops would hit hard at Hamas in Gaza.

"Israel will land a serious blow against the Hamas infrastructure in the Gaza Strip," he said, quoted by the AFP news agency.

In Nablus, two Palestinians were killed and nearly 30 wounded by army fire in a clash between soldiers and Palestinian gunmen and stone-throwers.

One of the wounded was in a coma and on life support, hospital officials said.

The clashes erupted as Israeli troops and tanks moved into the centre of the town to arrest Taysir Khaled, a member of the PLO executive committee.