Two explosions on Monday hit a pipeline which supplies Egyptian gas to Israel and Jordan, marking the 13th such attack in just over a year, security officials said.
Six gunmen in an unmarked vehicle set explosives in two different parts of the pipeline, about 15 metres (yards) apart, one official told AFP.
Witnesses said they heard two separate explosions, causing flames to shoot 20 metres (65 feet) into the air in the Al-Massaeed area, close to the town of El-Arish in north Sinai.
Emergency services were at the scene extinguishing the blazes, officials said.
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The pipeline only resumed operations last week after a similar blast on February 5 shut it down.
The pipeline, which supplies gas through Sinai and on to Jordan and Israel, had already been attacked 12 times since the uprising that ousted president Hosni Mubarak in February 2011.
Egypt has been gripped by security-related problems since the uprising. The Sinai peninsula is particularly sensitive because of tensions with the heavily armed Bedouin community living there.
Many goods are smuggled to the Palestinian enclave of the Gaza Strip through the Sinai, which the Israelis also charge is a rear base for militant attacks against its territory.