President Donald Trump said Thursday the United States is in no rush to end the war with Iran but "the clock is ticking" for the Islamic republic, as a third American aircraft carrier arrived in the Middle East.

Iranian media reported blasts over the capital Tehran, a first since an increasingly tenuous ceasefire in the Middle East war came into effect two weeks ago.

It was not clear what caused the explosions, although an Israeli security source told AFP that their country was not currently striking Iran.

WASHINGTON/DUBAI/ISLAMABAD, April 23 (Reuters) - Iran seized two ships in the Strait of Hormuz as it tightened its grip on the strategic waterway after U.S. President Donald Trump announced he was indefinitely calling off attacks, with no sign of peace talks restarting.

Global stocks mostly fell Thursday, retreating after recent gains as investors tempered their enthusiasm for a quick end to the Middle East war.

The benchmark international oil contract, Brent North Sea crude, rose further above $100 a barrel, rekindling fears of pervasive inflation that could dent economic growth around the globe.

Wall Street's main indexes finished lower after a volatile session, joining most markets in Europe and Asia in retreating.

April 23 (Reuters) - Ukraine could face increased risks in securing U.S. anti-missile defences if the war in Iran goes on for an extended period of time, Ukrainian President Volodymyr Zelenskiy said on Wednesday.

Zelenskiy, interviewed by CNN, said Ukraine received limited numbers of such weaponry because U.S. production was limited, but so far it had experienced no disruption in supplies or in provision of intelligence.

Zelenskiy said Ukraine was able to secure U.S. weaponry through the PURL programme under which NATO countries can finance the purchase of weapons for Kyiv.

Israel and Lebanon on Thursday extended a shaky ceasefire by three weeks, President Donald Trump announced Thursday, as he voiced hope for a historic three-way meeting soon and a potential peace deal.

Trump, at a standstill in negotiations with Iran, spoke in glowing terms of peace prospects for Lebanon, even as Hezbollah fired new rockets following deadly Israeli strikes.

By extending a ceasefire indefinitely with Iran, President Donald Trump appears to be searching for a way out of a costly war, but Tehran may be unwilling to give him a win.

Trump has insisted on maintaining a naval blockade, which Iran is demanding must end before it can consider any agreement to end the conflict launched on February 28 by Israel and the United States.

LONDON/NEW DELHI, April 22 (Reuters) - The U.S. military has intercepted at least three Iranian-flagged tankers in Asian waters and is redirecting them away from their positions near India, Malaysia and Sri Lanka, shipping and security sources said on Wednesday.

WASHINGTON, April 22 (Reuters) - President Donald Trump said on Wednesday that Iran had agreed not to execute eight women protesters in a sign of respect for him, while officials in Tehran denied the executions had been planned and accused the U.S. president of spreading falsehoods.

"Very good news," Trump said in a social media post a day after granting a unilateral ceasefire in the war started by the U.S. and Israel on February 28.

Trump said four of the eight women would be released immediately and four would be sentenced to one month in prison.

April 22 (Reuters) - President Donald Trump wants to see a "unified" response from Iran's leadership to U.S. proposals to end hostilities, White House press secretary Karoline Leavitt said on Wednesday.

Leavitt told reporters that Trump had not set a deadline for an end to the ceasefire extension he announced on Tuesday.

Earlier, Leavitt said in an interview with Fox News' "The Story with Martha MacCallum" that Iran must agree to turn over its enriched uranium to the United States as part of negotiations to end the war.

By Maya Gebeily

BEIRUT, April 22 (Reuters) - Israeli strikes in southern Lebanon wounded one journalist and left another trapped under rubble on Wednesday with rescuers temporarily blocked from reaching her by ongoing Israeli fire, Lebanon's health ministry, a senior military official and press advocates said.

Israel's military said in a statement it had received reports that two journalists were injured as a result of its strikes, and denied it was preventing rescue teams from reaching the area.