GAZA CITY (AFP) - Israel reacted on Tuesday to fighters' rocket fire by again sealing off the Gaza Strip, where officials said the territory's sole power plant was forced to shut down because of the crippling blockade. The renewed closure of the impoverished Palestinian enclave came one day after humanitarian supplies were allowed in for the second time since Israel tightened its blockade following a November 4 surge in violence. "After rockets were fired at the Israeli territory, Defence Minister Ehud Barak decided, following consultations with security services officials, that the crossing points will be closed on Tuesday," the defence ministry said in a statement. Palestinian fighters in the Gaza Strip fired a rocket at southern Israel on Monday, causing no casualties or damage, a military spokesman said. On Monday, 30 truckloads of humanitarian and other basic goods were delivered to Gaza. The Israeli authorities had previously opened the Kerem Shalom border crossing for only one day since violence flared up at the beginning of the month. Israel also opened the Karni crossing conveyor belt on Monday to deliver wheat and grain as well as the Nahal Oz terminal for the delivery of fuel to the power plant. But Israeli authorities have made it clear the crossings will open again only if Gaza fighters respect a truce that went into effect on June 19 but has been rattled by the upsurge in violence. The closure of the crossings has led to international concern over the plight of residents in the overcrowded sliver of land whose economy has been crippled by a blockade Israel imposed after the Hamas movement seized power in June 2007. On Tuesday, Gaza's sole power plant, which provides 25 to 30 percent of the energy used in the overpopulated territory, ground to a halt, according to Kanaan Obeid, assistant director of Gaza's energy authority. "Despite deliveries of fuel on Monday, the power plant stopped functioning because of breakdowns in the production units," he said. He said the frequent shutdowns of the plant caused by fuel shortages damaged parts of the production units that cannot be replaced because of the blockade. Israel "refuses to allow in the necessary parts and the plant cannot restart without them," he said. The power plant has been particularly hard hit by Israel's blockade, and Gazans regularly experience blackouts. Hamas says Israel has not been keeping its side of the truce deal by refusing to ease the blockade, while Israeli authorities insist Gaza fighters must first hold their fire. The Israeli defence minister has nevertheless come out in favour of an extension of the six-month truce. "In the months preceding the entry into force of the truce, we were recording as many as 500 mortar or rocket attacks a month in southern Israel against just a dozen in the months since the truce," Barak told parliament on Monday.