Two men were remanded in custody Sunday in connection with an attack outside the Israeli embassy in Belgrade that Serbian authorities called a "targeted terrorist act", a minister said.

The assailant, whom the police said was a "convert" to Islam, shot a Serbian police officer in the neck with a crossbow while he was on duty in front of the embassy early Saturday.

The officer then shot and killed the attacker.

The assailant, from Mladenovac, near Belgrade, lived in Novi Pazar, a historical and political centre of Serbia's Bosniak Muslim minority, police said.

At least once a day, the hum of every fan, air conditioner and fridge across Egypt goes quiet. The lights go out and an expletive is muttered or hurled into the quickly-heating air.

Lifts stop, errands are cancelled and meetings delayed for as long as the power stays out -- hopefully an hour or two, but recently even longer.

It is now a year since energy and foreign currency crises led Egypt's government to institute planned blackouts known as "load shedding".

But the measures have not been felt equally across the country.

A Serbian police officer on Saturday killed a man who shot him in the neck with a crossbow in front of the Israeli embassy in Belgrade, in what the prime minister called a "terrorist act".

Police identified the assailant as being a "convert" to Islam, who was born in 1999 in the town of Mladenovac, some 50 kilometres (30 miles) from Belgrade.

The attack happened around 11:00 am (0900 GMT) on Saturday in the Serbian capital, when the attacker shot the officer who was on duty outside the Israeli embassy.

Explosions, air strikes and gunfire rattled northern Gaza on Saturday, the third day of an Israeli military operation that has uprooted tens of thousands of Palestinians and compounded what the UN called "unbearable" living conditions in the territory.

An AFP correspondent reported explosions from the Shujaiya area near Gaza City, and a resident saying bodies were seen on the streets.

The armed wings of both Hamas and the Palestinian militant group Islamic Jihad said they were engaged in ongoing fighting with Israeli forces there.

Masoud Pezeshkian, Iran's sole reformist candidate, has risen from relative obscurity to leading the votes in the first round of the Islamic republic's presidential elections, stunning supporters and rivals alike.

Pezeshkian, 69, won the largest number of votes in a first round on Friday that saw him face off against three figures from the conservative camp, all vying to replace late president Ebrahim Raisi who died in a helicopter crash last month.

Ultraconservative former Iranian nuclear negotiator Saeed Jalili, who will face a reformist in a runoff for president, is widely recognised for his steadfast anti-Western stance.

Jalili, 58, will aim to unify Iran's fragmented conservative factions in the bid for the presidency when he faces Masoud Pezeshkian next Friday.

A relatively reserved figure with a well-groomed white beard and spectacles, Jalili will seek to persuade voters he is best suited to lead Iran under the guidance of supreme leader Ayatollah Ali Khamenei, who holds ultimate authority in the country.

The sole reformist in Iran's presidential election, Masoud Pezeshkian, will face the ultraconservative Saeed Jalili in a runoff, authorities said on Saturday, following a vote marred by historically low turnout.

Pezeshkian secured 42.4 percent of the vote, while Jalili, a former nuclear negotiator, came second with 38.6 percent, according to figures from Iran's elections authority.

Conservative parliament speaker Mohammad Bagher Ghalibaf was next with 13.8 percent, while the only other candidate, conservative cleric Mostafa Pourmohammadi, got less than one percent.

A United Nations agency said it has discovered five bombs in a wall of Mosul's iconic Al-Nuri mosque, planted years ago by Islamic State group jihadists, during restoration work in the northern Iraqi city.

Five "large-scale explosive devices, designed to trigger a massive destruction of the site," were found in the southern wall of the prayer hall on Tuesday by the UNESCO team working at the site, a representative for the agency told AFP late Friday.

Reformist candidate Masoud Pezeshkian and ultraconservative Saeed Jalili are leading in Iran's presidential election, according to early results on Saturday from the Interior Ministry.

According to the latest count, Pezeshkian has won more than 8,300,000 votes and Jalili, a former nuclear negotiator, has above 7,100,000

Should the current trend continue, both candidates would head into a runoff set for July 5. The second round is required if no candidate wins 50 percent of the vote, plus one.

Gazans are forced to live in bombed-out buildings or camp next to giant piles of trash, a United Nations spokeswoman said Friday, denouncing the "unbearable" conditions in the besieged territory.

Louise Wateridge from UNRWA, the UN agency supporting Palestinian refugees, described the "extremely dire" living conditions in the Gaza Strip.

"It's really unbearable," she told reporters in Geneva, via video-link from central Gaza.