British Foreign Minister Jeremy Hunt warned of “serious consequences” on Sunday, and is expected to announce a series of diplomatic and economic measures aimed at Iran, possibly including pushing for the renewal of E.U. and U.N. sanctions, as well as the freezing of Iranian assets in London, according to The Telegraph.

LONDON—British Prime Minister Theresa May was due to chair the government’s COBR emergency committee on Monday to agree a response to Iran’s seizure of a UK-flagged oil tanker.

The government has said that that the Stena Impero was in Omani waters when it was surrounded by four Iranian vessels and a helicopter, before being impounded by Iranian forces.

The seizure is believed to be a retaliation for the seizure by Britain of the Grace 1 supertanker off the straits of Gibraltar for carrying Iranian oil bound for Syria in violation of EU sanctions. The government has advised UK ships to avoid the Straits of Hormuz for a limited period.

British Foreign Minister Jeremy Hunt warned of “serious consequences” on Sunday, and is expected to announce a series of diplomatic and economic measures aimed at Iran, possibly including pushing for the renewal of E.U. and U.N. sanctions, as well as the freezing of Iranian assets in London, according to The Telegraph.

Following a telephone conversation with Iranian Foreign Minister Mohammad Javad Zarif, according to the BBC, Hunt said that Iran viewed the siezure of the Stena Impero as a “tit-for-tat” response to the detention of the Grace 1 by Gibraltar. “Nothing could be further from the truth,” said Hunt.