An explosion at the home of a Hamas activist in Gaza City Sunday has killed at least four Palestinians and wounded three others.

A huge crowd gathered at the scene in the Zeitnoun neighborhood of Gaza City, as Hamas activists prevented journalists from inspecting the ruins of the home.

A resident of the area said he was sitting on his balcony when he heard the blast and saw people covered in blood being evacuated from the building.

The cause of the explosion was not immediately known. In the past, there have been a number of incidents in which Palestinian militants preparing bombs have accidentally blown them up.

Hamas, the Islamic Resistance Movement, has launched numerous attacks including suicide bombings that have killed hundreds of Israelis.

The explosion comes one day after the military wing of Hamas claimed responsibility for the killing of four Israeli soldiers, after their tank drove over an explosive device in the Gaza Strip.

Israeli Defense Minister Shaul Mofaz, at a meeting of the Israeli Cabinet Sunday, threatened tough action against the Hamas.

Meanwhile, there was more violence in the West Bank Sunday. At least one Palestinian was killed and eight others wounded in exchanges of fire in Nablus between Israeli soldiers and Palestinian gunmen.

The fighting erupted after Israeli troops surrounded a building in the city and began arresting suspected Palestinian militants.

Residents said Palestinian gunmen began shooting in an attempt to prevent the soldiers from continuing door-to-door searches and the troops returned fire.

Earlier Sunday, Israeli troops arrested a top member of the military wing of Palestinian leader Yasser Arafat's Fatah faction.

Salah Al-Aryah, a suspected arms dealer, was picked up in the West Bank town of Tulkarem. Israel had wanted him for alleged involvement in a number of terror attacks and the theft of machine guns from an Israeli army base.