Campaigning opened Saturday in Egypt for a presidential election likely to be won by the ex-army chief who deposed an elected Islamist leader, after deadly bombings underscored tensions gripping the country.

The May 26-27 presidential poll, meant to restore elected rule following the military overthrow of Mohammed Morsi last June, is widely expected to place former army chief Abdel Fattah al-Sisi in power.

Rolling blackouts have already been hitting neighborhoods of Cairo daily throughout the winter, when electricity usage is lower. Now summer's heat is coming, and Egypt's crippling energy crisis is threatening to mount, creating an immediate political liability for the new president to be elected this month.

The government is scrambling to reduce the impact.

Bombers killed a policeman and a soldier in Egypt Friday, hours before campaigning starts for presidential polls which the former army chief who deposed an elected Islamist leader is expected to win.

Militants have unleashed a wave of attacks targeting security forces since the military ousted president Mohammed Morsi last July, while security forces have waged a deadly crackdown on Morsi's supporters and his Muslim Brotherhood movement.

About 300 illegal immigrants abandoned by people traffickers in the scorching Sudanese-Libyan desert, where several died, will be escorted to a Sudanese town from Friday, the army said.

Army spokesman Sawarmi Khaled Saad told Agence France Presse the migrants, who were receiving medical care, would be taken by local Sudanese officials to the northern town of Dongola on the Nile River.

French Foreign Minister Laurent Fabius Wednesday criticized Egypt for imposing death sentences on nearly 700 suspected Islamists.

"These sort of slaughter sentences are absolutely unacceptable," Fabius told French lawmakers.

A senior U.S. senator has moved to block hundreds of millions of dollars in aid to Egypt to protest the death sentences imposed on nearly 700 suspected Islamists.

Denouncing Egypt's "dictatorship run amok" and its "egregious violation of human rights," Democrat Patrick Leahy, who heads the Senate subcommittee overseeing foreign aid appropriations, said he is putting a hold on the $650 million in military aid greenlighted by the Pentagon last week.

An Egyptian judge jailed Muslim Brotherhood leader Mohammed Badie and 21 others for a year Wednesday for insulting the court during a trial in which ousted president Mohammed Morsi is also a defendant.

Earlier, Badie had lashed out against another court's death sentence against him and 682 alleged Islamists, insisting that the "coup" that toppled the Islamist Morsi would be defeated.

A Qatar-based Sunni Muslim group led by influential cleric Sheikh Yusef al-Qaradawi has condemned as "politicized" an Egyptian court's decision to sentence hundreds of Islamists to death.

The court on Monday imposed death sentences on 683 suspected Islamists -- including Muslim Brotherhood leader Mohamed Badie -- amid a crackdown on supporters of ousted Islamist president Mohamed Morsi.

Egypt's military-installed leaders must prove they are serious about bringing democracy to the world's largest Arab nation, U.S. Secretary of State John Kerry insisted Tuesday.

He delivered the stern warning as he met with Foreign Minister Nabil Fahmy -- the highest level visit to Washington by an Egyptian official since the army ousted elected Islamist leader Mohammed Morsi in July, throwing U.S. policy towards Cairo into disarray.

The German foreign ministry said it summoned the Egyptian ambassador Tuesday to urge the lifting of 683 death sentences handed down by an Egyptian court to suspected Islamists.

The ministry said its Middle East coordinator Volkmar Wenzel had made the "urgent appeal" to Ambassador Mohamed Higazy for the justice authorities to reverse Monday's decision "and allow the affected people to have a fair trial."