Iran won't ignore maritime offences: Zarif

Iran Foreign Minister Mohammad Javad Zarif has warned his country could leave the 2015 nuclear deal

Iran's foreign minister says his country will no longer turn a blind eye to "maritime offences" in the Gulf, a day after it seized an Iraqi oil tanker there that it accused of smuggling fuel.

Revolutionary Guards seized the tanker and its seven crew near Iran's Farsi Island north of the Strait of Hormuz, state media reported, in a show of power amid heightened tension with the West that minister Mohammad Javad Zarif blamed US authorities for fomenting.

"Iran used to forgo some maritime offences in ... (the) Gulf but will never close (its) eyes anymore," Zarif told a news conference.

He criticised US sanctions imposed on him on Wednesday, saying Washington had closed the door to diplomacy over Iran's 2015 nuclear deal, which US President Donald Trump exited last year.

"Sanctioning a foreign minister means failure in talks," Zarif said.

Tehran has threatened to block all exports via the Strait, though which a fifth of global oil traffic passes, if other countries heed US calls to stop buying Iranian oil.

Zarif said European powers still party to the nuclear deal should accelerate efforts to salvage it, though Iran would leave the pact if necessary.

Oil tanker traffic through Hormuz and other strategic waterways has become a focus for the stand-off between Washington and Tehran, into which Britain has also been dragged.

Fuelling fears of a Middle East war with global repercussions, the Guards seized British tanker Stena Impero near the Strait of Hormuz in July for alleged marine violations, two weeks after British forces captured an Iranian oil tanker near Gibraltar accused of violating sanctions on Syria.

Zarif called the UK seizure "piracy" and said the Gulf's security was Iran's responsibility.

"(The) UK government has been complicit in the US economic terrorism against Iran," he said.

In June, Iran downed a US drone near the Strait, prompting preparations for a US retaliatory air strike that Trump called off at the last minute.