A ceasefire declared by US President Donald Trump between Israel and Iran is being put to the test in its early hours, after a missile fired into Israel prompted accusations of a breach.

Shortly after Trump declared an end to the 12-day war, Israel said it had detected a missile launch from Iran. Defense Minister Israel Katz instructed the military on Tuesday to “respond forcefully to Iran’s violation of the ceasefire with powerful strikes against regime targets in the heart of Tehran.”

Iran denied it fired missiles at Israel after the ceasefire came into force, according to the state-run IRIB news agency, which didn’t elaborate.

The fragile truce followed an extraordinary night in which Tehran retaliated against a US attack over the weekend by launching missiles at an American air base in Qatar. The Islamic Republic’s move was telegraphed — with Qatar and the US being forewarned — and there were no casualties.

“THE CEASEFIRE IS NOW IN EFFECT,” Trump said at around 9:10 a.m. Dubai time on Truth Social. “PLEASE DO NOT VIOLATE IT!”

Prime Minister Benjamin Netanyahu later confirmed Israel agreed to a truce and said his country had achieved its war goals in Iran.

Oil prices plunged when it became clear Iran’s strikes on Qatar caused no fatalities or major damage. Traders took it as a sign that Iran had no intention of escalating tensions with Washington, let alone drag other countries in the oil-rich region into a wider war.

Sentiment in oil markets remained optimistic. Brent fell 3.4% to around $69 a barrel on Tuesday, following a drop of more than 7% on Monday. It returned to the level before Israel started attacks on Iran on June 13.

“If the ceasefire holds – and there is no guarantee that it will — it will undoubtedly be greeted positively by markets as it will at the margin reduce uncertainty,” said Daniel Murray, chief executive officer of EFG Asset Management in Switzerland. Lower oil prices will reduce inflationary pressure and “also help support consumption trends and hence growth overall.”

Israel struck targets in Iran early on Tuesday, but the explosions in Tehran seemed to stop at about 4 a.m. local time, the BBC reported, citing local residents. Iranian Foreign Minister Abbas Araghchi said around the same time the Islamic Republic did not intend to continue attacks if Israel’s stopped.

While Israeli officials remained silent overnight, a senior White House official said Trump brokered the ceasefire in a direct conversation with Netanyahu on Monday. Vice President JD Vance, Secretary of State Marco Rubio and special envoy Steve Witkoff held direct and indirect talks with the Iranians about the proposal, the official said.

Israel agreed to the truce as long as Iran did not launch further attacks, and the Iranian government signaled it would abide by those terms, according to the official.

The developments came about two days after the US entered the conflict directly by bombing key Iranian nuclear facilities at Fordow, Natanz and Isfahan. Trump said the strikes “completely and totally obliterated” the sites, though battle damage assessments continue and the whereabouts of Iran’s enriched uranium stockpile is unknown.

Qatar said the Iranian missile barrage was intercepted and the base had been evacuated in advance.

Iran’s move on Monday appeared to be “a largely symbolic retaliation,” said Ziad Daoud, Bloomberg Economics’ chief emerging-market economist. “Plenty of warning was given — Qatar shut its airspace and the US issued warnings to citizens” in the gas-rich country.

While Iranian state TV said the missile barrage “forced a ceasefire on the enemy,” some Iranian officials suggested the move contained a performative element. The number of missiles fired matched the number of bombs deployed by the US against the nuclear sites.

Iran was quick to say that Qatar, which has strong relations with Tehran as well as Washington, is a “friendly and brotherly country.”

A diplomat briefed on the talks said Trump had spoken with Qatar’s Emir Sheikh Tamim bin Hamad Al Thani and informed him the US got Israel to agree to a ceasefire. Trump asked the Qatari leader for help persuading Iran to do the same. Iran later agreed, according to the diplomat, who asked not to be identified discussing private conversations.

Many questions remain, including the state of Iran’s uranium stockpile and whether any ceasefire will lead to discussions about Tehran’s nuclear program. The Islamic Republic, which has denied it’s seeking an atomic weapon, has refused to give up the right to enrich uranium, a condition the US has insisted upon.

Iran says it needs to process uranium at least to the low level needed for civilian purposes such as fueling nuclear power plants. Yet the West and Arab states are wary because Iran has enriched the uranium almost to the levels needed to build a bomb, without explaining why.

Speaking to Fox News after Trump announced the ceasefire, Vance said the US bombing over the weekend had met its objectives.

“We know that they cannot build a nuclear weapon,” Vance said, adding that Iran’s existing stock of highly enriched uranium was “buried” by the attack. International monitors have said they don’t know where that material is after Iran said earlier this month it would move it.

“If Iran is desperate to build a nuclear weapon in the future, then they’re going to have to deal with a very, very powerful American military,” Vance said.