Iran has warned Britain to avoid making "any new mistake" following the detention of the British ambassador to Tehran.
Ambassador Rob Macaire said he was briefly detained on January 11 after attending a vigil for the victims of last week's downing by Tehran of a Ukrainian passenger jet in Iran -- some of whom were Britons.
Iran's Foreign Ministry said on January 11 that it had "summoned" Macaire to complain about "his unconventional behavior of attending an illegal rally."
Britain on January 13 summoned the Iranian ambassador to the country, Hamid Baeidinejad, to protest Macaire's detention.
Prime Minister Boris Johnson's spokesman told reporters on January 13 that the government would convey its "strong objections" about the detention, calling it an "unacceptable breach" of the Vienna Convention governing diplomatic relations.
"We are seeking full assurances from the Iranian government that this will never happen again,” the spokesman said.
After the meeting with Baeidinejad, Iran's Foreign Ministry issued a warning.
"Any new mistake of Britain will be severely confronted by Iran and London will be responsible for that," the ministry said, according to Iranian state TV.
The statement added that Macaire's presence at the vigil was "against diplomatic norms."
Macaire tweeted that he left the vigil after 5 minutes, when some people started chanting.
On the same day, Iranian protesters set a British flag on fire in front of the Tehran embassy.