KHAN YOUNIS, Gaza Strip >> Israel closed the main commercial crossing in the Gaza Strip, effectively banning exports from the coastal territory after saying it had uncovered explosives in a shipment of clothes to the occupied West Bank. Gaza’s fishermen, with their perishable exports, were among the first to feel the pain.

The new restrictions choke off the territory’s already ailing economy. They come on top of the punishing 16-year blockade that Israel and Egypt have maintained since the Islamic militant group Hamas seized control of the enclave in 2007.

The blockade, which Israel says is needed to prevent Hamas from arming, severely limits the movement of people and goods in and out of Gaza.

Israel closed the Kerem Shalom cargo crossing late on Monday after saying it had discovered explosives hidden in a shipment of Zara jeans and other clothing bound for the West Bank — one of the main markets for Gaza’s tiny export sector. Israeli officials fear the explosives were bound for Palestinian militants in the West Bank. Israel has not said when the crossing will reopen.

Palestinian fishermen, businessmen and rights advocates condemned Israel’s latest measure as a form of collective punishment against Gaza’s 2 million people, including tens of thousands of laborers who heavily depend on exports to Israel and the West Bank to stay afloat. Nearly all the goods that enter and exit Gaza pass through Kerem Shalom.

Gaza’s 4,000 fishermen, worried about keeping their surplus seafood from spoiling, condemned the ban.

“Now I can’t make a living,” said Khalid al-Laham, 35, from his bare home in the southern town of Khan Younis as his five children scurried around him. “I have to borrow food from the shops.”

The struggle also reached Gaza’s wealthiest traders.

“Fish are completely different from any product, it’s sensitive,” said Mohammed Abu Hasira, a 38-year-old owner of a popular Gazan fish restaurant near the Mediterranean. “They should punish those who are at fault. Why are we being punished with them?”

Abu Hasira’s plans to export truckloads of fish Thursday were thwarted by the Israeli decision, he said. Within moments, his profits evaporated and costs skyrocketed.

Overall, the measure has caused 26 tons of fish to rot and resulted in $300,000 in weekly losses, Gaza’s main fishermen’s union said.

The restrictions represented a reversal of recent Israeli military moves to ease the blockade to relieve economic pressure on Gaza to prevent tensions from boiling over into another bloody conflict.

Israel now allows some 21,000 Palestinian laborers from Gaza to enter Israel for work, and in July, Israel issued hundreds more permits. Some 70% more people left the strip in July than during the same month last year, according to the United Nations humanitarian office.

But now Gaza’s fishermen and others affected by the Israeli measure said they’ve again been subsumed into a larger political struggle that has nothing to do with them.

Israel says the closure was intended to deter militants from sneaking explosives through the crossing and to press the strip’s Hamas rules to crack down on the smuggling.

“The defense establishment will not allow terror organizations to take advantage of civilian and humanitarian facilities,” Israel’s defense ministry said.

The move, rights groups said, also laid bare Israel’s inability to provide an effective answer to the security incidents and to address Gaza’s underlying problems.

“Instead of finding proportionate and reasonable measures, it just imposes sweeping measures and punitive closings,” said Miriam Marmur, a spokeswoman for Gisha, an Israeli human rights group.

Under the blockade, Gaza’s businessmen have grappled with what they describe as exasperating bureaucratic controls and routine indignities.

Fishermen say their struggle reflects how the blockade has damaged a vital part of Gaza’s economy. In July, fish accounted for 6% of all exports, according to the U.N.

The restrictions have prevented them from importing engines, fiberglass, and other materials needed to repair their dilapidated boats.

The naval blockade limits how far out into the Mediterranean Sea the fishermen can go — and how much and what type of fish they can catch. If they drift too close to Israel’s maritime border, they risk being shot at or having their boats seized by the Israeli navy.

Since the start of the year, the U.N. humanitarian office, or OCHA, has recorded over 400 incidents in which Israeli forces opened fire at Palestinian fishermen approaching the sea boundary, causing injuries and damage. “Recurring shootings off the coast of Gaza are deeply troubling,” said Noel Tsekouras, head of OCHA’s Gaza office. “These actions severely jeopardize livelihoods.”

This week’s closure has left all merchants reeling in the crowded enclave. In an upscale tower just blocks from the seaport, Muhammad al-Ghussein, an engineer and spokesperson for the Palestinian Businessmen Association, said he shared the fishermen’s concerns.

“Halting exports is like dealing a fatal blow to a sector that’s already dying,” he said.