The Iranian army has shot down an unidentified foreign drone near the port of Bandar-e Mahshahr on the Gulf coast, according to reports from the country’s news agencies.

The unmanned aircraft was downed over Iranian territory with domestically manufactured Mersad surface-to-air missiles. Provincial governor Gholamreza Shariati told agencies that the drone belonged to a foreign country and that parts of it had been recovered in a nearby lagoon. Iranian news agencies said the drone was shot down in the country’s airspace. The US has denied that the drone was theirs.

The seriousness of the latest episode will largely depend on the ownership of the drone, and whether it was for military or civilian purposes. The port is the leading hub for Iranian activity in the Gulf, as well as a petrochemical facility. Iran has claimed to have shot down drones before, only for further news on the incidents not to be made public.

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In June, US president Donald Trump authorised a strike on Iran after an American drone was shot down, only to call off the attack at the last minute amid fears that it would lead to excessive civilian casualties. In that episode, Washington said the aircraft was in international airspace, but Iran maintains it was over its territorial waters.

The US has been responding to the escalating tensions with a military build-up in the Gulf and on Thursday launched a new operation with its allies from Bahrain to protect navigation in Gulf waters. The Iranians, with Russian support, are touting a rival plan to bring peace to the Strait of Hormuz, involving its regional partners.

Shariati said: “At the moment, the debris of the UAV (unmanned aerial vehicle) is being pulled out by the military and security forces and experts have begun investigating it.”

He added: “The UAVs are definitely a foreign ’country’s and the results of the expert reviews will be made public after they are determined.”

“It is clear that this drone has entered the Mahshahr area without coordination, so the city’s defence has attempted to overthrow it.”

The episode comes as the main European powers – France, Germany and the UK – prepare to issue a fresh statement objecting to the Iranian decision to pull back further from the nuclear deal signed in 2015. Iran announced plans this week to inject uranium gas into centrifuges in its Fordow nuclear facility.

The EU statement is not expected to call on the EU powers to pull out of the deal despite the successive steps by Tehran. Foreign affairs ministers from Europe are expected to discuss the issue next week.