Saboteurs blew up a pipeline that runs through Egypt's North Sinai, state television said, disrupting flows to Israel and Jordan, after Islamists called on militants to exploit the unrest that has rocked the government.
State television quoted an official on Saturday as saying that the "situation is very dangerous and explosions were continuing from one spot to another" along the pipeline.
"It is a big terrorist operation", a state TV reporter said.
A security source in North Sinai said "foreign elements" targeted the branch of the pipe that supplies Jordan.
Gas supplies halted
A security source said the Egyptian army closed the main source of gas supplying the pipeline and were controlling the fire. Television footage showed a tower of flame at the scene.
Jordan said gas supplies from Egypt were expected to remain halted for a week until the pipeline was repaired.
A Jordanian energy source told Reuters the kingdom had switched power stations to burning fuel oil and diesel as a precaution, after the cut-off of the Egyptian gas supplies that help generate most of Jordan's electricity.
Israeli officials said Egyptian natural gas supplies to Israel were suspended.
"We are looking into all the details but it is too soon to say how long supplies (from Egypt) will be affected," a source in the Israeli National Infrastructure Ministry told Reuters.
The attack happened as demonstrations against President Hosni Mubarak entered their 12th day, with no sign of an end to the confrontation which has pitted the 82-year-old leader against thousands of anti-government protesters.
"Saboteurs took advantage of the security situation and blew up the gas pipeline," a state television correspondent said.
The SITE intelligence group, which monitors al-Qaeda and other Islamist websites, said some groups had been urging Islamic militants to attack the pipeline to Israel.
"Jihadists suggested that Muslims in Sinai take advantage of Egyptian unrest and strike the Arish-Ashkelon gas pipeline, arguing that it would have a major impact on Israel," SITE said.
Israel gets 40 percent of its natural gas from Egypt, a deal built on their landmark 1979 peace accord.
The company that supplies Egyptian gas to Israel is East Mediterranean Gas (EMG), and one of the major shareholders in the company is Mubarak associate and former Egyptian intelligence chief Hussein Salem.
Opposition groups have long complained that Egyptian gas is sold to Israel at preferential prices and that the contract with EMG violated bureaucratic regulations. The government insists it is done on commercial terms and everything is in order.
Egypt is a modest gas exporter, using pipelines to export to Israel, Jordan and other regional states. It also exports via liquefied natural gas facilities on its north coast, but those are not in the Sinai region.
The North Sinai source said the attack was carried out by "foreign elements".
"We are now relying on Bedouin leadership in the areas surrounding to help security apparatus with the investigation and give us hints of any other destructive acts," he said.
Egypt declared a high state of alert in the area, another security source said. Gunmen opened fire on a governorate building in North Sinai but no casualties were reported. Abdel Wahhab Mabrouk, the area's governor, told state TV: "By closing the taps they contained the fire and we assure the people there are no human losses. It is an act of sabotage."
Residents in the area reported a huge explosion and said flames were raging near the pipeline in the al-Arish area.
SITE quoted one Islamist website author as saying: "To our brothers, the Bedouins of Sinai, the heroes of Islam, strike with an iron fist because this is a chance to stop the supply to the Israelites."
Sinai Bedouins have long grumbled about being neglected and have sporadically clashed with Egyptian security forces. Many Bedouin were rounded up after a series of explosions in Sinai tourist resorts between 2004 and 2006.
Israel's Yam Tetis field off coastal Ashkelon was prepared to help compensate for the loss of Egyptian gas and "disruptions to (Israeli) electricity production are not expected", the National Infrastructure Ministry said in a statement.
Israeli Prime Minister Benjamin Netanyahu said on Friday his country planned to draw increasingly on its own gas fields.
Egypt supplies about 40 percent of Israel's natural gas, and in December, four Israeli firms signed 20-year contracts worth up to $10 billion (€7.4 billion) to import Egyptian gas.
The attack came after Israel expressed concern that its natural gas supplies from Egypt could be threatened by the anti-regime uprising.
"We again realize that the Middle East is not a stable region. We must act to ensure our energy security without relying on others," a spokesman for National Infrastructure Minister Uzi Landau said on Tuesday.
Israel is concerned that a new regime in Cairo might not respect the peace treaty the two governments signed three decades ago -- and with it, the crucial energy supplies.
A broad swathe of Egypt's opposition, including the powerful Muslim Brotherhood, as well as public opinion has called for Cairo to stop supplying Israel with gas.
Landau on Monday summoned the heads of Israeli companies that are developing the offshore Tamar gas field -- due to start production in 2013 --to urge them to push ahead with its timely development, his office said.
Landau told them Tamar's importance was even greater "in these times of unrest in our region." The Tamar field, off the port city of Haifa in northern Israel, holds reserves estimated at eight billion cubic metres (280 billion cubic feet).
The Globes financial newspaper reported that Landau's ministry had conducted exercises dealing with emergency scenarios in which gas supplies were cut off. It gave no further details.
Egypt is a modest gas exporter, using pipelines to export gas to Israel and also to Jordan and other regional states. It also exports via liquefied natural gas (LNG) facilities on its north coast, but those are not in the Sinai region.
Mubarak, who has pledged to step down in September, said on Thursday he believed Egypt would descend into chaos if he were to give in to protesters' demands that he quit immediately.
He has styled himself as a bulwark against Islamist militancy and essential actor in maintaining a peace treaty Egypt signed with Israel in 1979.
Al-Qaeda, which has ideological roots in Egypt, has been largely sidelined in the protests against Mubarak.
The government in the past has used a perceived threat from Islamist militancy to justify its use of emergency laws which helped keep Mubarak in power.