According to an Interior Ministry statement, Wednesday's bombs, which followed three deadly explosions in the east Sinai resort of Dahab on Monday, killed only the bombers.
A spokesman for the Multinational Force and Observers (MFO) group, which supervises the Israeli-Egyptian peace treaty, said the first bomber appeared to single out for attack two of its vehicles but there were no MFO injuries.
The MFO, which has contingents from 11 countries, was set up to supervise security provisions in the 1979 peace treaty.
It patrols the Egyptian-Israeli border to ensure that the treaty is observed.
The second man blew himself next to a police car outside a police station in Sheikh Zuwayed, near the northern coast town of El Arish.
The car was empty and there were no other casualties, security sources said.
It was not immediately clear if all the incidents were related, but most members of the group blamed for attacks in Sinai over the past two years came from El Arish area.
The office of the governor of Sharkia province in the east of the Nile Delta meanwhile denied reports of a third incident in the town of Bilbeis.
Police sources had earlier said a group of armed men ambushed policemen in Bilbeis, leading to an exchange of fire.
An Interior Ministry statement gave a different version of the two explosions in north Sinai and said one was by a bedouin on a bicycle carrying a bomb.
It said a police officer was leaving El Gorah airport, where the MFO has its main base, when he saw a man carrying a bomb.
Foreigers were among 18 people
killed in Monday's triple blasts
The bomb exploded as the officer's car passed, smashing the windscreen but causing no casualties, it said.
When two police officers left the North Sinai police headquarters to investigate the first incident, the Bedouin on the bicycle tried to obstruct them with a bomb, it said.
"The bomb blew him up and he died and the explosion had no other effect," the statement added.
Police sources had said that two policemen were injured in the first explosion.
The three almost simultaneous bombs in Dahab on Monday killed 18 people, including four foreigners, and injured scores.
The Dahab explosions resembled other attacks attributed to a Sinai-based group which has bombed two other resorts on the east coast over the last two years.
The same group is thought to have attacked an MFO vehicle in Sinai in August, slightly injuring two Canadians.
Police have detained more than 80 people for questioning over the Dahab explosions, but no one has been charged.