Unidentified gunmen attacked a terminal along the Egyptian natural gas pipeline to Israel in the northern Sinai Peninsula on Saturday, marking the third such attack this month and the fifth since the ouster of former Egyptian President Hosni Mubarak in February.

After the attack on the pipeline and a separate weekend attack on a police station in the port town of El-Arish, Egyptian security sources told Israel Hayom that the new government in Cairo was losing control over part of the peninsula.

According to reports, gunmen launched rocket-propelled grenades at the al-Shulaq natural gas terminal, hitting the pipeline that directs gas to Israel and Jordan. The line, which has not been repaired since a previous attack on July 12, did not contain any gas.

Reuters reported that the attackers initially tried to storm the area's main gas station, but fled after being confronted by security forces.

No casualties were reported in the pipeline attack.

After the July 12 attack on the pipeline, Israeli National Infrastructure Minister Uzi Landau said the sabotage symbolized the deterioration of the “central pillar anchoring Israel's peace treaty with Egypt -- the economic pillar.”

“From the economic perspective, the peace agreement between Israel and Egypt is crumbling,” Landau said at the time, adding that the consequence of the repeated attacks on the pipeline delivering gas to Israel would be an increase in the cost of Israeli electricity.

In a related development, Egyptian state media reported that at least six people were killed and at least 21 were injured in unrest that began Friday, when more than 100 armed men rode into the town of El-Arish in Sinai and tried to storm a police station. Authorities said some of the attackers waved flags bearing Islamic slogans as they fired shots into the air.

Other reports said some of the attackers shouted slogans calling for the Sinai to be turned into “an Islamic emirate.”

Witnesses told the French news agency AFP that the armed men had also tried to destroy a statue of former President Anwar Sadat, who was assassinated by Islamists in 1981.

State-run news agency MENA reported that the dead included a policeman and a military officer.

Egyptian authorities said on Saturday that 15 of the attackers were arrested, including 10 Palestinian nationals. Their names were not publicly released.

Meanwhile, hundreds of thousands of Islamists packed Cairo's Tahrir Square on Friday in a show of force that angered secularists as clashes in Sinai between security personnel and apparent Islamists killed four, including a military captain, AFP reported.

Islamists from across the country flocked into the central square to defend what they called “Egypt's Islamic identity” in the country's largest protest since Mubarak’s ousting in February.

The rally in Cairo, organized by hardline Salafi groups and the influential Muslim Brotherhood, came as tensions grow between secular activists and the military on the one hand and Islamists on the other.

“The people demand the application of God's law,” thousands chanted under the searing sun, many of them carrying umbrellas or pouring water on their heads to counter the heat.