A Gaza company that operates water desalination plants serving nearly half of the enclave's population has stopped operations to protest at the detention by Hamas of one of its staff.
Youssef Yassin, a board member of the Abdul Salam Yassin Company, said the move would affect more than 1 million people who normally receive water from the company.
Over 70 trucks that carry water containers across the enclave have also stopped operations, he added, risking further supply disruption after the pipeline network was badly damaged during the war.
"I know it is catastrophic but protecting our employees is a sacred issue," Yassin told Reuters.
Yassin said Hamas had given no reason for the arrest late on Monday. Hamas had no immediate comment when contacted by Reuters on Tuesday.
Hamas has been gradually reasserting control in areas of Gaza that Israel has withdrawn from as post-war talks over its future grind on. Foreign powers demand the group disarm and leave government, but have yet to agree who will replace them.
Israel continues to control around half the Gaza Strip.
The move is a rare show of dissent against Hamas, which has run the Palestinian enclave since 2007. Demonstrations briefly erupted in March and April, demanding an end to the war and that Hamas give up power, but fizzled out after a warning that public disorder would not be tolerated.
If the protest by the company persists, it could exacerbate the chronic water crisis in the enclave, which was worsened further by two years of war.
Israel stopped all water and electricity supply to Gaza early in the war but resumed some supplies later.
Most water and sanitation infrastructure has been destroyed and pumps from the aquifer often rely on electricity from small generators, for which fuel is rarely available.
