Egyptian President Mohamed Morsi appealed Wednesday to the opposition for unity, in the face of criticism he is failing the revolution that brought him to power almost a year ago.

"To all those who love Egypt, to the opposition, those who love this country and care for its interests, let's proceed together... help each other, love each other more... and move forward," said Morsi.

 Kidnappers on Wednesday released three Egyptian policemen and four soldiers seized in the Sinai, the army said, leading to the reopening of a Gaza border crossing that police closed to protest the abductions.

"The seven security personnel have been released by their kidnappers in Sinai," military spokesman Ahmed Aly said in a statement carried by Egypt's official MENA news agency.

Egyptian troops and policemen began sweeps of north Sinai on Tuesday ahead of a possible showdown with heavily armed gunmen who abducted seven security personnel, officials said.

A senior interior ministry official told Agence France Presse a "campaign has been going on for half an hour", while a policeman taking part in the operation told AFP that security forces traded fire with gunmen in a village in the restive peninsula.

Egypt sent police reinforcements to the Sinai after an attack on a police camp on Monday in the wake of the kidnapping of security personnel, officials said.

In Cairo, the presidency said all options were on the table to secure the release of the three policemen and four soldiers held last week in the lawless peninsula.

Egypt's liquor stores are under growing pressure to stop selling alcohol, they say, not from the country's Islamist government, but from society itself.

The shelves of Amir Aziz's central Cairo premises are stacked with beer, wine and spirits, but they are invisible from the street.

A Palestinian youth was killed when a tunnel linking Egypt to the Gaza Strip collapsed on Saturday, Palestinian medical sources said.

"Mussa Ghonaim, 26 years old, was killed in the tunnel collapse south of the town of Rafah," the sources said.

Demonstrators calling for Egypt's Islamist President Mohamed Morsi to resign and demanding early elections clashed with riot police in Cairo late Friday.

Hundreds of people had marched on Cairo's Tahrir Square on Friday for the protest, called by a number of opposition groups.

More than 1.5 million Syrians have fled their conflict-ravaged homeland, the U.N.'s refugee agency said Friday, warning that the real figure could be even higher as the tally only reflected those who register with aid groups.

Dan McNorton, spokesman for the U.N. High Commissioner for Refugees, told reporters that close to 250,000 Syrians were being registered each month.

Egyptian police closed the Rafah border crossing with Gaza on Friday in protest at the kidnapping of colleagues in the Sinai peninsula, a security source and witnesses said.

Three policemen and four soldiers were abducted on Thursday by armed men who are demanding the release of a group of prisoners held at a police station in the North Sinai town of El-Arish, official media reported.

Egyptian President Mohammed Morsi on Thursday summoned his defense and interior ministers over the kidnapping hours earlier of policemen and soldiers in the Sinai peninsula, the official MENA agency reported.

The crisis talks at the presidential palace come after unidentified gunmen kidnapped three Egyptian policemen and four soldiers in the lawless Sinai peninsula, security officials said.