A Palestinian youth visiting jailed relatives in the Gaza Strip stabbed four Israeli jailers Friday and seriously wounded three of them before being subdued, a prison spokesman said.

Soldiers arrested the 17-year-old after a chase outside the Gaza Central Prison, said Johnny Tester, the prison spokesman. He said the assailant's brother is a prison inmate. Tester and Israel radio said the assailant is believed to be a member of the underground fundamentalist group Islamic Jihad.In the West Bank city of Nablus, troops wounded two youths in a clash with Palestinian demonstrators who hurled rocks and bottles in the city's open-air market, hospital officials and Palestinian witnesses said.

Police and soldiers closed Jerusalem to Palestinians from the occupied territories to prevent violent protests called for by underground leaders during Moslem prayers at the city's Al Aqsa mosque.

The leaders called for a "day of confrontation" at the mosque, one of the holiest sites of Islam, and police poured hundreds of reinforcements into Jerusalem, doubling the city's normal police force.

Since the uprising broke out Dec. 8 in the territories Israel seized in the 1967 Middle East war, 215 Palestinians and four Israelis have been killed.

Ilana Ziv, a spokeswoman at Barzilai Hospital in Ashkelon, said two of the jailers hurt in the prison attack were rushed to the hospital by helicopter, and one was in serious condition with stab wounds to the heart. Israel radio said two others were taken to Tel Aviv's Tel Hashomer Hospital, where one was in moderate condition and the other lightly wounded.

The radio said the assailant carried two knives and the attack appeared to have been plotted in advance.

The army said it was investigating.

In Nablus, Palestinians heeded a general strike called for by underground Islamic fundamentalist leaders. Arabs in the city blocked roads with rocks, burned tires and ordered merchants to close their shops, Palestinian reporters said.