Foreign secretary Jeremy Hunt said the government had come to the conclusion after its “own assessment” of Thursday’s incident.
He said in a statement on Friday: “I condemn yesterday’s attacks on two vessels in the Gulf of Oman.
“These latest attacks build on a pattern of destabilising Iranian behaviour and pose a serious danger to the region.
“In targeting civilian shipping, international norms have been violated.
“It is essential that tankers and crews are able to pass through international waters safely.”
Mr Hunt called on Iran to urgently cease all forms of destabilising activity.
The Iranian mission to the United Nations dismissed US claims that it was behind the attacks earlier on Friday.
It said in a statement: “Iran categorically rejects the US unfounded claim with regard to 13 June oil tanker incidents, and condemns it in the strongest possible terms.”
Dozens of crew members had to be rescued after the Norwegian-owned MT Front Altair and the Japanese-owned Kokuka Courageous were evacuated near the Strait of Hormuz on Thursday.
Images shared by Iranian media showed the super tankers ablaze in the sea.
The US sent two guided missile destroyers, USS Mason and USS Bainbridge, to the scene of the attacks to protect the vessels.
An Iranian tugboat was reportedly waved off by USS Bainbridge when it attempted to tow Kokuka Courageous.
The owner of the Japanese tanker claimed US reports of the attacks provided “false” information about what happened.
The ship operator said “flying objects” that may have been bullets were the cause of damage to the vessel, rather than mines used by Iranian forces, as the US has suggested.
Yutaka Katada said the damage could not have been caused by mines or torpedoes that are shot underwater, since the damage was reportedly above the ship’s waterline.
“It seems that something flew towards them. That created the hole, is the report I’ve received,” Mr Katada told a press conference in Tokyo on Friday, the Financial Times reported.
Mr Katada also described reports of a mine attack as “false” according to several outlets in attendance at the press conference.
UN secretary-general Antonio Guterres said it was important to find out the truth about what happened and called for an independent investigation into the suspected attacks.
Japanese prime minister Shinzo Abe said Japan “adamantly condemns” the attack, “no matter who attacked”.
Meanwhile, the Russian foreign ministry warned against rushing to assign blame until the completion of a “thorough and unbiased international probe”.
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