A 17-year-old Arab high school student was killed and three others wounded today when an Israeli Army patrol opened fire on angry demonstrators who had surrounded it, the Army command said.

Israeli authorities said a five-man patrol in the Gaza Strip town of Rafah, south of this Israeli-occupied city, had been stoned by students in a demonstration by several hundred Arabs about noon, and that the soldiers fired warning shots in the air before firing at the demonstrators.

An Army command spokesman said Mohammed Salem Abu Tachle, 17, was fatally wounded, and that three other students, two aged 16 and one 14, were wounded. The spokesman said one soldier was injured when youths threw stones at the patrol and attemped to beat the soldiers.

Earlier, the demonstrators set fire to a car, Israeli authorities said. Fifty students were arrested of whom 15 were still detained tonight.

Arab officials of Rafah, which lies on the Mediterranean coast of the northern edge of the Sinai Peninsula, were summoned to the regional military commander's office and warned that if they used the incident to incite further demonstrations, the Army would retaliate.

An Army command spokesman said that the patrol had "acted according to standing orders," but that because a fatality was involved, the military police would conduct an investigation.

Security was tight in the Gaza Strip today as schools, factories and shops remained closed in a week-long general strike called to protest the Israeli government's decision to impose a value-added tax on sales.

The strike began last week with 1,000 physicians, lawyers, pharmacy owners and engineers. Then the mayor of Gaza City, Rashid Shawa, broadened the protest to include opposition to the recently imposed Israeli civilian administration in the military government. The disturbances spread today from Gaza City to Rafah and Khan Yunis, the other major town in Gaza.

In Gaza City, virtually every shop was shuttered at noon today when an Israeli Army mobile acetylene unit moved from shop to shop welding shut the steel doors of striking merchants.

In one block, Arab merchants scurried to reopen. But as the truck-hauled acetylene unit moved systematically down the main street, dozens of other merchants simply stood and watched as the doors to their shops were welded shut. Normally, the military government forbids shopkeepers to reopen until 50 days after the doors are welded.

Demonstrating youths in Gaza City also burned tires and pelted Israeli patrol vehicles with stones.