The newspaper's website said that the raised alert levels were a response to an overnight attack by Islamist gunmen on an airport in the Sinai town of El-Arish."We were already very prepared in this important strategic region," a military source said. "The announcement is just to assure our soldiers and people that we are ready in Sinai. As for Suez we are always on an alert state there."The head of the Suez Canal Authority, who oversees the key world trade route, said it was operating normally with no disruption to cargo traffic. Mohab Mameesh said 48 ships had passed through the canal on Friday. Al-Ahram had reported that raised alert levels were in response to an overnight attack by Islamist gunmen on an airport in the North Sinai town of El-Arish.The report quoted the commander of the Third Field Army Osama Asakar saying that the "state of readiness" had been raised to its highest level in the two provinces due to the attack.The attack, the latest of a string of security incidents in the lawless region, came two days after the overthrow of Islamist President Mohamed Morsi. It was not clear if the attacks were coordinated and in reaction to his removal. Egypt has closed the Rafah border crossing with the Gaza Strip on Friday indefinitely. Gaza is controlled by the Islamist organization Hamas. Maher Abu Sabha, director of border crossings in Gaza says Egypt told Hamas of the indefinite closure. The Egyptian director of the Rafah terminal, Sami al-Mitwali, said the crossing was closed due to security unrest, Palestinian news agency Ma'an reported. Nilesat an Egyptian company, that controls a series of Egyptian communications satellites, removed Hamas TV al Quds from the air in recent days.In the Friday attack, the security sources said a soldier was killed and two were wounded when a police station in Rafah on the border with the Gaza Strip came under rocket fire. The police post is close to the local headquarters of military intelligence.Earlier, attackers fired rocket-propelled grenades at army checkpoints guarding El-Arish airport, close to the border with the Gaza Strip and Israel, in the latest of a string of security incidents in the lawless region, the sources said.A military helicopter fired a missile at one of the vehicles trying to attack the airport, Israel Radio reported. No casualties were reported as a result of the missile attack. It was not clear whether the attacks were coordinated and in reaction to Morsi's removal. Islamist militants believed to have links to al-Qaida have established a foothold in the sparsely populated desert peninsula, sometimes in league with local Beduin smugglers and with Palestinian terrorists from Gaza.Egypt has struggled to control security in the region since the ousting of autocratic President Hosni Mubarak in 2011.Yaakov Lappin, Ben Hartman and Khaled Abu Toameh contributed to this report