People attend a protest against the U.S attack on nuclear sites, amid the Iran-Israel conflict, in Tehran, Iran, June 22, 2025. Majid Asgaripour/WANA (West Asia News Agency) via REUTERS

By Andrew Mills, Parisa Hafezi and Alexander Cornwell

DOHA/ISTANBUL/TEL AVIV (Reuters) -Explosions were heard over Qatar's capital Doha on Monday, a Reuters witness reported, shortly after a Western diplomat said there had been a credible Iranian threat against the U.S.-run al Udeid air base in the Gulf Arab state since midday.

The diplomat spoke soon after Qatar announced it had closed its air space temporarily to ensure the safety of residents and visitors. Earlier, the U.S. embassy in Qatar had advised Americans to shelter in place, out of what it said was "an abundance of caution".

A satellite view shows an overview of Fordow underground complex, after the U.S. struck the underground nuclear facility, near Qom, Iran June 22, 2025. MAXAR TECHNOLOGIES/Handout via REUTERS

Iran has issued threats to retaliate against the United States after U.S. bombers dropped 30,000-pound bunker-busters on the country's underground nuclear installations over the weekend, while President Donald Trump openly raised the possibility of the Iranian government being toppled.

A U.S. Air Force B-2 stealth bomber returns after the U.S. attacked key Iranian nuclear sites, at Whiteman Air Force Base, Missouri, U.S. June 22, 2025 in a still image from video. ABC Affiliate KMBC via REUTERS

Earlier on Monday, Israel struck a jail for political prisoners in Tehran in a potent demonstration that it was expanding its targets beyond military and nuclear sites to aim squarely at the pillars of Iran's ruling system.

Two U.S. officials said Washington assessed that Iran could carry out attacks targeting American forces in the Middle East soon, although the U.S. is still seeking a diplomatic resolution that would see Tehran forgo any reprisal.

Satellite image shows an overview of Isfahan Nuclear Technology Center, before it was hit by U.S. airstrikes, in Isfahan, Iran, June 16, 2025. Maxar Technologies/Handout via REUTERS

Despite Iran's threats to challenge oil shipments from the Gulf, oil prices largely held steady, suggesting traders doubted the Islamic Republic would follow through on any action that would disrupt global supplies.

A boy rides a scooter near a damaged car at an impact site following Iran's strike on Israel, amid the Iran-Israel conflict, in Haifa, Israel, June 22, 2025. REUTERS/Florion Goga

Iranian Foreign Minister Abbas Araqchi met Russian President Vladimir Putin in Moscow as Tehran sought backing from one of its last major power friends for its next steps.

(Reporting by Reuters; writing by Peter Graff; editing by Bernadette Baum and Mark Heinrich)