The Egyptian army launched an attack against Islamist militants in North Sinai on Saturday, killing at least nine people, security officials said.
Two Egyptian soldiers were killed late on Saturday when an improvised explosive device detonated in a road in the North Sinai town of Sheikh Zuweid near the border with the Gaza Strip, security sources said.
Radical Islamists in the rugged desert region adjoining Israel, who expanded into a security vacuum left by the overthrow of Hosni Mubarak in 2011, have been staging almost daily assaults on security forces and other targets.
Dozens of tanks and armoured vehicles backed by attack helicopters were used earlier in Saturday's operation near Sheikh Zuweid, a few miles from the Palestinian Gaza Strip, security sources said.
The army said nine militants had been arrested.
Since the army toppled Islamist President Mohamed Morsi on July 3, and especially since security forces killed hundreds of Islamists when they smashed protest camps in Cairo on Aug. 14, there have been online calls from Islamist radicals for wider attacks on the state.
Egyptian memories of an Islamist insurgency in the 1990s were revived on Thursday when a suicide bomber blew up a car bomb next to the interior minister's convoy in Cairo.
On Saturday, a bomb exploded at a Cairo police station for the second time in less than a week, state media said, although no one was hurt.
In addition, explosives were found on the railway line between the cities of Suez and Ismailia along the Suez Canal, but defused before they could do damage, according to the state news agency MENA.
No one has claimed responsibility for any of the attacks, although a video apparently of the Suez attack was posted on YouTube with an Islamist logo.
But the army-backed rulers have incensed Islamists inside Egypt and abroad with their violent crackdown on Morsi's Islamist movement, the Muslim Brotherhood, most of whose top leaders have been arrested and accused of terrorism or inciting violence.
The Brotherhood, sworn to peaceful resistance, dismisses the accusations as a pretext for the crackdown by a "putschist regime", and has defied the crackdown to bring thousands onto the streets across Egypt three times in eight days.
The military-backed government now also appears to be turning its sights on other groups - opposed to the Islamists - who helped topple Mubarak in 2011 hoping to establish an open civilian democracy in Egypt.
A judicial source said the public prosecutor was examining complaints from private citizens against 35 prominent democracy and rights activists, many of them important players in the 2011 uprising.
They include activist Ahmed Maher, blogger Ahmed Douma and liberal politician Amr Hamzawi, the judicial source said.
Such prosecutions have long been seen as a tool of political intimidation in Egypt and are often instigated by supporters of the government. Liberal politician Mohamed ElBaradei, who was deputy president in the interim government before resigning, has been targeted in a similar case.
The latest complaints accuse activists of accepting money from the United States and other countries, the source said.
Hamzawi said on Twitter that "claims that I got foreign money are completely untrue, the campaign of fabrication and distortion must immediately stop".
"These are fake accusations," rights lawyer Gamal Eid told Reuters. "(The complaint) is from people who know that it is false but who try to silence activists' demands for the realisation of the demands of the revolution."
The prosecutor's office was not available for comment on the issue.
Separately, a leftist lawyer accused of belonging to a secret organisation and spreading lies about the military appeared before military prosecutors in Suez, but was later released, judicial sources said.
Haitham Mohamedeen, a rights activist who belongs to the Revolutionary Socialist movement, a group critical of the army, had been arrested in Suez on Thursday. It was not clear whether the case against him had been dropped.
Egyptian journalist Ahmed Abu Deraa also remained in detention after his arrest in North Sinai on Wednesday.
The military prosecutor accused him of spreading lies and giving military information to secret organisations, a source at the prosecutor's office said.
"The detention of Ahmed Abu Deraa harks back to the Mubarak era, when journalists faced formidable obstacles reporting on military activity in the Sinai peninsula," said Robert Mahoney, deputy director of the Committee to Protect Journalists.