Russia and the UK have denied offending Iran over a controversial photo of their ambassadors in Tehran.
An image of the two diplomats sat on the historic steps of the 1943 Tehran Conference sparked anger from Iranian authorities.
Russian ambassador Levan Dzhagaryan and his British counterpart Simon Shercliff were pictured on the same steps where allied leaders had met during World War II when Iran had been invaded.
The Russian Embassy has stated that the image was only intended to commemorate the fight against Nazi Germany.
But Iran has described the photo as "extremely inappropriate" and summoned the two ambassadors, according to state media.
Why is the image controversial?
Dzhagaryan and Simon Shercliff were pictured sat atop the same stairs where Soviet leader Josef Stalin met UK Prime Minister Winston Churchill and US President Franklin Roosevelt in 1943.
The so-called Tehran Conference of the "Big Three" leading powers was intended to strengthen their countries' cooperation against Nazism.
In their original tweet, the Russian embassy also noted the comparison between the photo and the 1943 conference, although Roosevelt's seat was left empty.
Although officially neutral in World War II, Iran was considered supportive of the Axis powers, and in 1941, Soviet and British troops invaded largely unopposed to secure oil fields and Russian supply lines through Iran.
Eighty years on, Iranian officials have stated that reminders about their foreign occupation are an attack on their country's diplomatic sovereignty.
The outgoing foreign minister, Mohammad Javad Zarif, said on Twitter that the picture of the two ambassadors on the same steps was "extremely inappropriate".
Zarif drew a connection between the photo and the stalled negotiations with world powers over Iran’s nuclear programme.
"The Iranian people have shown ... that their destiny can NEVER be subject to decisions in foreign embassies or by foreign powers," he said.
The Speaker of the Iranian Parliament, Mohamad Baqer Qalibaf, also tweeted that the picture was "inappropriate" and called on Russia and the UK to apologise or risk "a decisive diplomatic response" from Iran.
'No anti-Iranian context'
In response to the criticism, the Russian embassy has reiterated that they meant no offence to Tehran and said the photo had "no anti-Iranian context".
"We were not going to offend the feelings of the friendly Iranian people," the embassy said on Twitter.
"The only meaning that this photo has [is] 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."
Tehran and Moscow have improved their relations in recent decades after Russia built Iran’s sole nuclear power plant in the southern Iranian port of Bushehr.
The two countries have also increased military cooperation, and Russia delivered hundreds of thousands of vaccines to Iran to fight COVID-19.
The statements by the Russian Embassy were also retweeted by the UK ambassador Shercliff from his personal account.
Tensions between Iran and Britain have risen over an attack last month on a Liberian-flagged tanker off the coast of Oman.
A British national and Romanian citizen were killed in what the UK has described as an "unlawful and callous" drone strike.
Iran has denied any involvement in the incident and says the accusations are "baseless".