Staff from the Palestinian prime minister's office went on strike Wednesday, joining a widespread work stoppage by civil servants demanding overdue salaries from the Hamas-led government. The strike was especially embarrassing to Prime Minister Ismail Haniyeh of Hamas, who has been leading opposition to the walkout. Hamas accuses the rival Fatah party of orchestrating the strike, which has emerged as a formidable challenge to a government already embattled by international sanctions and widespread anarchy. As the strike shut down much of the Palestinian territories for a fifth day, Israel pressed forward with a military offensive in the Gaza Strip. Six Palestinians, at least five of them Hamas militants, were killed. The Palestinian government has been in a financial crisis since Hamas took over in March after winning parliamentary elections. Hamas, which calls for the destruction of Israel, has refused international pressure to renounce violence and recognize the Jewish state. In response, Western donors and Israel have cut off aid and transfer payments. Without the foreign funds, the government has been unable to pay regular salaries to its 165,000 workers for months, instead handing out small, sporadic stipends. Seeking a way out of the crisis, President Mahmoud Abbas, a moderate who leads Fatah, has been urging Hamas to soften its positions and ally with it in a national unity government. Hamas has accused Fatah of using the strike as a pressure tactic in coalition talks. Fatah, which ruled Palestinian politics for decades, still dominates labor unions and security forces. The 30 workers in Haniyeh's office who joined the strike on Wednesday were Fatah loyalists. Even so, the open defiance of their boss embarrassed the premier. The workers, joining dozens of other striking civil servants, held up banners that said, "We want our salaries. We have a right to feed our children." Hamas had no immediate comment. The strike has enjoyed only lukewarm support in Gaza, a Hamas stronghold, though several thousand security men rampaged in downtown Gaza City on Tuesday. The shutdown has been much more effective in the West Bank, shutting down schools and emptying hospitals. In some places, the strikes have been enforced by pro-Fatah gunmen. In the West Bank town of Jenin, about 1,000 people marched in favor of Hamas on Wednesday, chanting in support of Haniyeh. In the nearby city of Nablus, Fatah and Hamas activists nearly came to blows when Nabil Amr, a top Fatah official, gave a speech to about 450 people at a local university. "From the time Hamas took power, life has declined and Hamas has no solutions," Amr told the crowd.