Iran said it was once again closing the vital Strait of Hormuz shipping lane on Saturday over Israel's attacks in Lebanon, calling them a violation of its deal with the United States to end the Middle East war.

Israeli warplanes conducted deadly strikes in Lebanon's south on Saturday, hours after the United States announced a renewed ceasefire in the fighting there, killing at least 28 people.

The ongoing Israeli attacks had already strained the deal signed by the US and Iran this week to halt the wider regional war on all fronts — including in Lebanon, which had been a key demand for Tehran.

Citing a US "breach of contract" and "the Zionist regime's continuous and relentless violation of the ceasefire in southern Lebanon", Iran's central military command announced on Saturday that “the Strait of Hormuz will be closed to vessel traffic."

Deal in ‘trouble’

Separately, Iran's foreign ministry said that the agreement signed between Iran and the United States to halt the Middle East war will be "in trouble" unless its provisions are implemented soon.

"The other side must take the necessary measures as soon as possible. Otherwise, the entire understanding will be in trouble," ministry spokesperson Esmaeil Baqaei said, according to the official news agency IRNA.

The strait, an important conduit for oil and gas shipments, was blockaded by Iran for much of the war, sending shockwaves through global energy markets.

Iran had agreed to reopen it under the preliminary agreement with the US, and shipping traffic was starting to pick back up in recent days.

Follow-up talks on the US-Iran deal had been planned in Switzerland on Friday, but were indefinitely postponed as Israel launched a wave of deadly strikes in Lebanon after four of its soldiers were killed in combat.