Israel sealed off the West Bank and Gaza Strip completely on Friday after defense chiefs warned that the radical Palestinian Islamic group Hamas planned to carry out a major attack.

The closure added to a mood of tension ahead of a crucial visit next week by U.S. Secretary of State Madeleine Albright to try to break a deadlock in peace moves between Israeli leader Benjamin Netanyahu and Palestinian President Yasser Arafat.The announcement coincided with renewed unrest in the divided West Bank city of Hebron, where Palestinian hospital staff said seven youths had been wounded, one seriously, by rubber bullets in clashes with Israeli soldiers.

The center of Hebron has been under an Israeli curfew since Wednesday when 13 Israeli soldiers and border police were wounded in a grenade attack by suspected Palestinian militants.

The Israeli army said security chiefs would decide early next week whether to extend the closure. Israel starts an eight-day period of Jewish holidays on Sunday evening.

Israel has restricted access to Palestinian workers from the West Bank and Gaza to varying degrees since September 10, when its forces shot dead two leading Hamas militants near Hebron.

The latest blanket closure brought a dismayed response from Palestinian officials, who said it would sour the atmosphere before Albright's two-day visit starting next Tuesday.

Her talks are meant to pave the way for a mid-October summit in the United States at which President Bill Clinton wants to seal a deal on the transfer by Israel of more West Bank land to Palestinian rule and on tougher Palestinian security steps.

Chief Palestinian negotiator Saeb Erekat called the closure "collective punishment as if we don't have a peace process.

"This . . . is one of the major obstacles to creating trust between the two sides," Erekat said.

Hamas has killed dozens of Israelis in suicide bombings since the 1993 Oslo interim peace accords, but has not carried out a major attack since September 1997.