A suicide bomber blew himself up on a crowded bus in the northern Israeli coastal city of Haifa, killing at least 15 people and wounding dozens of others.

The explosion occurred early afternoon local time as bus number 37 was driving through the Karmaliya neighborhood of Haifa.

The blast was massive and initial television footage from the scene showed the wreckage of the smoldering bus with its roof torn off. Debris and bodies were strewn over the street as emergency personnel rushed to the scene.

One distraught witness said the explosion occurred just after the bus had reached a stop. He said he had just gotten off the bus and walked away when he heard the blast. Officials said because of the time of attack and the route, the bus would likely have been filled with students from nearby Haifa University.

A spokesman for the Islamic militant group Hamas praised the attack, but did not claim responsibility.

Palestinian militants have carried out numerous attacks and suicide bombings against Israeli targets since their uprising against the Israeli occupation began two and a half years ago. This was the first such attack in two months. In early January a suicide bomber killed more than 20 people in Tel Aviv.

Prime Minister Ariel Sharon's office blamed Palestinian leader Yasser Arafat for the Haifa attack and a spokesman called it another example of Palestinian bloodletting against innocent Israeli civilians. Mr. Arafat has condemned the bombing and rejected the accusation that he is responsible.

Palestinian Information Minister Yasser Abed Rabbo issued a statement condemning the Haifa attack, which he said only serves to distract attention from the many Palestinian civilians killed in Israeli security operations in the last two months.

The Israeli military has re-occupied most Palestinian population centers in the West Bank and has launched a major military operation in the Gaza Strip in the last few weeks.

Israeli police are reported on heightened alert throughout the country after the Haifa attack. In the past Israel has responded to such attacks with tough military measures.