Egyptian troops were "on alert" in the Sinai Peninsula, a military spokesman said on Friday, but he denied a report by the state-owned Al-Ahram newspaper that a state of emergency had been declared in Suez and South Sinai provinces.
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.
Early on Friday, Islamist gunmen staged multiple attacks on security forces in Sinai two days after the Egyptian army overthrew elected Islamist President Mohamed Mursi.
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.
It was not clear whether the attacks were coordinated and in reaction to Mursi's removal.
Islamist militants believed to have links to al Qaeda have established a foothold in the sparsely populated desert peninsula, sometimes in league with local Bedouin smugglers and with Palestinian militants from Gaza.
Egypt's prosecutor general tendered his resignation on Friday, three days after being reinstated in his post following the removal of an appointee of the ousted president.
Originally appointed by Hosni Mubarak, Abdel Meguid Mahmoud was forced out after the Islamist Mursi was elected a year ago, prompting a long legal battle. Mursi's Muslim Brotherhood complained that its efforts to govern were being hampered by Mubarak loyalists in the judiciary and other state institutions.
An appeals court reinstated Mahmoud on Tuesday, forcing the removal of Mursi's appointee Talaat Abdullah, whom the liberal opposition had accused of bias toward the Islamist government. Mursi was deposed by the armed forces on Wednesday.
Mahmoud, who was close to Mubarak and a target of anger during the 2011 uprising, could also have expected criticism from the liberals now working with the military authorities to form an interim government. The state news agency MENA said Mahmoud would request a transfer to a judge's post.
His departure clears the way for an appointment to be made under interim head of state Adli Mansour, the chief justice of the constitutional court.