Reuters - Iran will severely respond if Britain makes �new mistakes,� Iranian Foreign Ministry said in a statement on Monday, a day after Tehran briefly detained the U.K envoy for attending an �illegal� rally.

�Any new mistake of Britain will be severely confronted by Iran and London will be responsible for that. The presence of the UK envoy is against diplomatic norms... Threatening Iran with fresh sanctions over that will cause tension between Tehran and London,� the statement said, according to state TV.

Writing by Parisa Hafezi; Editing by Chris Reese