The White House insisted Monday evening that US forces remained in a "defensive" posture in the Middle East, despite a military buildup over the Israel-Iran war and a shock warning from President Donald Trump to evacuate Tehran.

Trump's brief warning on social media, without further details, raised speculation that the United States may be readying to join Israel in attacking Iran.

Those suspicions rose further after it was announced that Trump would be leaving a G7 summit in Canada and returning to the White House a day early over the mounting Middle East conflict.

Britain is deploying extra fighter jets and other assets to the Middle East amid the escalating conflict between Israel and Iran, UK Prime Minister Keir Starmer has said.

Below, AFP takes a look at the UK's military presence in the region.

- 'Contingency support' -

Starmer told reporters travelling with him on his plane to Canada for G7 talks on Saturday that Britain was "moving assets to the region, including jets... for contingency support".

The jets are Eurofighter Typhoon planes, according to Britain's defence ministry.

Leading Iranian activists and filmmakers on Monday called for an end to hostilities between Iran and Israel, urging Tehran to stop the conflict by halting its enrichment of uranium.

"We demand the immediate halt of uranium enrichment by the Islamic Republic, the cessation of military hostilities, an end to attacks on vital infrastructure in both Iran and Israel, and the stopping of massacres of civilians in both countries," said the activists in an op-ed in French newspaper Le Monde.

Iran's supreme leader, Ayatollah Ali Khamenei, has weathered a series of challenges but Israel's unprecedented strikes mark his most serious crisis yet, threatening both the clerical system he leads and his own physical survival.

Khamenei, Iran's top leader since the death of Ayatollah Ruhollah Khomeini in 1989, has ruled in the face of sanctions, near constant international tensions as well as protests that were ruthlessly repressed, most recently the 2022-2023 women-led uprising.

Geopolitical tensions roiled the opening of the Paris Air Show on Monday as French authorities sealed off Israeli weapons industry booths amid the conflicts in Iran and Gaza, a move that Israel condemned as "outrageous".

The decision added drama to the major aerospace industry event, which was already under the shadow of last week's deadly crash of Air India's Boeing 787 Dreamliner.

Black walls were installed around the stands of five Israeli defence firms at the trade fair in Le Bourget, an airfield on the outskirts of Paris.

After an Iranian strike early Monday gouged a gaping hole in his apartment building in central Israel, Idan Bar said he feared for his family as the air war between the longtime foe escalated.

A tangle of metal protruded from the charred section of a high-rise building in Petah Tivka near Tel Aviv, as rescuers wheeled elderly residents away from the damage.

One woman's mouth hung open as she was taken away in a wheelchair.

"My building got bombed from Iran," Bar told AFP.

Israel and Iran traded deadly fire for a fourth day on Monday in their most intense confrontation in history, fuelling fears of a drawn-out conflict that could engulf the Middle East.

The longtime foes have fought a prolonged shadow war through proxies and covert operations, with Israel battling several Iran-backed groups in the region, including Hamas in the Gaza Strip since October 2023.

Here are the latest developments:

- Mounting casualties -

France on Monday blocked access to the stands of five Israeli arms manufacturers at the Paris Air show for displaying "offensive weapons", according to a French government source.

A black wall blocked off stands run by Israel Aerospace Industries (IAI), Rafael, Uvision, Elbit and Aeronautics for showing "offensive weapons", including those used in Gaza, which allegedly violated terms made with Israel, said the source.

Rafael, Elbit and IAI produce guided bombs and missiles, while Uvision and Aeronautics produce drones.

Prime Minister Benjamin Netanyahu insisted on Monday that Israel's campaign against Iran was "changing the face of the Middle East", as the two countries traded heavy strikes for a fourth day.

The remarks came hours after a dramatic attack on an Iranian state TV building, which forced a presenter to flee mid-broadcast and prompted a threat of retaliation against Israeli news channels.

A German court on Monday handed a life sentence to a Syrian doctor who tortured opponents of former ruler Bashar al-Assad during the country's brutal civil war.

The higher regional court in Frankfurt found Alaa Mousa, 40, guilty of crimes against humanity, committed while working as a doctor at military hospitals in Homs and Damascus between 2011 and 2012.

Mousa's actions were "part of a brutal reaction by Assad's dictatorial, unjust regime", presiding judge Christoph Koller said as he read out the verdict.