As part of Operation Chivalrous Knight 3, food, shelter tents, and basic supplies were provided to Palestinian families
The UK defence ministry said only that the Iranian boats tried to "impede" a commercial vessel called British Heritage, which is owned by British energy giant BP.
"Contrary to international law, three Iranian vessels attempted to impede the passage of a commercial vessel, British Heritage, through the Strait of Hormuz," the UK defence ministry said in a statement.
"HMS Montrose was forced to position herself between the Iranian vessels and British Heritage and issue verbal warnings to the Iranian vessels, which then turned away."
It also urged "the Iranian authorities to de-escalate the situation in the region".
Iran's Revolutionary Guards denied trying to seize or impede the UK tanker.
The episode adds further fuel to a volatile mix of brinkmanship and sabre rattling in a region already unsettled by the Trump administration's nuclear standoff with the Islamic Republic.
Iran has been ramping up uranium enrichment in response to the Trump administration's decision last year to pull out of a landmark nuclear agreement world powers signed after a decades of talks with Tehran in 2015.
It surpassed one limit set in that deal one month ago and breached a second one on Monday.
As part of Operation Chivalrous Knight 3, food, shelter tents, and basic supplies were provided to Palestinian families
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