The flames shot into the air as dawn broke
It is the second such attack in a month on the pipeline, south of the town of El-Arish, just 30 miles (50km) from the border with Israel.
On that occasion, when gunmen planted explosives, they failed to detonate.
"An unknown armed gang attacked the gas pipeline," an unnamed security source told Reuters, adding that the flow of gas to Israel and Jordan had been hit.
Neighbouring Jordan depends on Egyptian gas to generate 80% of its electricity while Israel gets 40% of its natural gas from the country. Syria also imports gas from Egypt.
Any disruption would force Jordan to rely on more expensive diesel fuel.
The valves controlling the flow of gas from the main terminal in Port Said, on the Mediterranean coast, were shut down to dampen the flames and people living nearby were forced to leave their homes.
However, there have been no reports of casualties.Continued