Iran has sharply criticised the Russian and British ambassadors to Tehran after a picture was posted online of the pair recreating a Second World War image from when Iran was under Soviet-Anglo occupation.
The picture shows Britain's new ambassador, Simon Shercliff, meeting Russian envoy Levan Dzhagaryan on steps leading to the current Russian embassy.
The photo, tweeted on Wednesday by the Russian embassy, shows the pair seated in a setting reminiscent of the 1943 Tehran conference meeting between British prime minister Winston Churchill and Soviet leader Joseph Stalin.
Churchill and Stalin, allies against Nazi Germany during the Second World War, were holding strategy talks with US president Franklin Roosevelt two years after the Anglo-Soviet invasion of Iran.
The picture drew sharp criticism from politicians across the board in Iran, including departing Foreign Minister Javad Zarif.
"I saw an extremely inappropriate picture today," Mr Zarif tweeted.
"The Iranian people have shown ... that their destiny can never be subject to decisions in foreign embassies or by foreign powers."
Hossein Amir-Abdollahian, his nominated successor, tweeted that the British and Russian envoys had "humiliated public opinion" in Iran
Iran's Foreign Ministry said on Thursday it had "invited" Mr Shercliff and Mr Dzhagaryan to attend, as it was seeking "clarifications" over the picture.
The ministry said the Russian envoy voiced "regrets" over the misunderstanding caused by the picture.
The Russian embassy said on Twitter that the picture was not intended to be offensive to Iran.
"Taking into account the ambiguous reaction to our photo, we would like to note that it does not have any anti-Iranian context," it said on Thursday.
"We were not going to offend the feelings of the friendly Iranian people."
It said the picture was an effort to "pay tribute to the joint efforts of the allied states against Nazism during the Second World War".
"Iran is our friend and neighbour, and we will continue to strengthen relations based on mutual respect," the Russian embassy said.
In 1941, Britain and the Soviet Union invaded Iran to secure oilfields and use its railroads for the Soviets fighting the Nazi-led Axis forces in Europe.
Tehran had already announced its neutrality in the war.
Iranians suffered during the occupation with food, fuel and other essentials becoming scarce amid mounting inflation, especially when the needs of invading powers were given priority.