Israeli security forces broke an eight-day commercial strike by Arab shopkeepers here today by welding shut the doors to scores of businesses and threatening mass prosecutions. Palestinian nationalist leaders continued to chafe under the new governing authority for the occupied territories and the imposition of an Israeli sales tax.

Egypt complained that measures being taken by Israel's military rulers in the occupied West Bank and Gaza Strip are "not conducive" to Palestinian participation in Middle East peace negotiations.

A Foreign Ministry spokesman in Cairo said Egypt has explained repeatedly to the Israeli government that "concrete measures" are needed to ease tensions in the occupied territories. He spoke after an Egyptian technical committee left for Tel Aviv to resume autonomy negotiations.

As Army patrols with two acetylene units moved slowly up and down Gaza's main commercial street today looking for the few remaining shops that had closed but had not already been welded shut, Arab merchants scurried to open their steel shutters to avoid either a forced closing for 50 days or being charged with a security violation that could bring five years' imprisonment.

Palestinian leaders said it was the harshest crackdown on a commercial strike in the Gaza Strip or the West Bank since Israel occupied the territories in the 1967 six-day war.

Israeli military authorities said they used the technique of welding shut the shopkeepers' steel doors as a deterrent against further illegal strikes and as a punishment for those merchants who heeded calls by militant nationalists to shut down the commerce in Gaza City.

"It works. You saw how it works," a spokesman for the Army command said, noting that most of the city's stores had reopened by late afternoon. Approximately 200 Arab shops were welded shut in a three-day military operation that covered virtually the entire city.

The military government maintains that if merchants are allowed to close their businesses with impunity, the disobedience of regulations forbiding strikes will spread to schools and other segments of the society and lead to chaos.

Defense Minister Ariel Sharon ordered the head of the recently imposed civilian administration in Gaza, Brig. Gen. Yosef Luntz, to implement the crackdown to end civil disobedience that in recent days had spread from Gaza City to the rest of the densely populated strip. As the strike spread, similar protests were held in the West Bank as a display of support of the Gaza movement.

The confrontation began two weeks ago when Gaza physicians and pharmacists objected to the imposition of a 12 percent Israeli value-added tax, saying it is illegal under the 1949 Geneva Convention for an occupying authority to impose new taxes. The Gaza medical society now has an appeal before Israel's Supreme Court.

Shopkeepers and the municipality joined the general strike when Army troops welded shut several pharmacies, and the conflict spread to a series of demonstrations, including one in nearby Rafa, where a 17-year-old student was shot dead by a soldier and two other students were wounded when an Israeli patrol was confronted by violent demonstrators.

After Gaza shops began reopening today, the medical society met with officials of the military government and agreed to end its strike as long as physicians and pharmacy owners are not prosecuted. The military government also agreed to hold the sales tax in abeyance until the court decides the issue.

Although the Gaza strike began as a protest of the Israeli tax, that issue quickly became secondary to a general resistance to the installation on Nov. 1 of the new Israeli civilian administration under the military government. The separation of civilian and military functions in Gaza and the West Bank is part of Sharon's plan to prepare the way for autonomy -- a provision of the Camp David peace process that many Palestinian leaders reject.

Gaza Mayor Rashid Shawa called the new civilian authority a "trick" to perpetuate the Israeli occupation and noted that the military governor still controls all of the civil functions of the occupation government.

Strikes were reported in several West Bank towns today, along with numerous rock-throwing incidents and student demonstrations.