Denmark announced Wednesday that it was consulting with its allies about possible sanctions against Iran after it uncovered on Tuesday a Tehran plot to target Iranian dissidents living in the Scandinavian country.
"We are going to reach out to our European allies in the coming days to try to find a united response," Danish Prime Minister Lars Lokke Rasmussen told reporters during a meeting of Northern European leaders in Oslo.
British Prime Minister Theresa May expressed her support for Denmark at the meeting.
Danish Foreign Minister Anders Samuelsen was to begin contacting his European counterparts on Wednesday to discuss possible sanctions against Iran -- most likely economic ones, a diplomatic source told AFP.
"We want to preserve the nuclear agreement," Lokke Rasmussen said, referring to how possible sanctions would approach the 2015 international accord on Iran's nuclear program.
Denmark on Tuesday announced it was recalling its ambassador to Iran after the Danish intelligence service PET accused the Iranian intelligence service of "planning an attack in Denmark" against three Iranians suspected of belonging to the Arab Struggle Movement for the Liberation of Ahvaz or ASMLA.
A Norwegian of Iranian origin was arrested on October 21 for planning the attack and spying for Iran.
Iran has denied the allegations, saying they were part of a European conspiracy against it.
Tehran summoned the Danish ambassador on Wednesday, foreign ministry spokesman Bahram Ghasemi said.
"In this meeting the (senior foreign ministry) official strongly denied the biased reports on a foiled attack plot on an Iranian dissident in Denmark and its attribution to the Islamic republic of Iran," Ghasemi said.
US Secretary of State Mike Pompeo said Wednesday Iran is the leading actor conducting assassination attempts in Europe.
"That kind of behavior needs to stop, and we have offered our support and effort to help the Europeans in preventing these kinds of assassination attempts from taking place," he told Fox News Radio.
In Oslo for a meeting of the Nordic Council, Northern European leaders were prudent.
"We are looking at the situation in Denmark as being very serious and not least because there is a Norwegian of Iranian descent involved," Norway's Prime Minister Erna Solberg said.
Her government had not yet decided what it would do pending a Norwegian police probe, she added.
"We are following this very closely together with our Danish friends and when we know more we will make a decision about possible measures," Swedish Prime Minister Stefan Lofven said.
In September, Tehran accused Denmark, along with the Netherlands and Britain, of "hosting several members of the terrorist group" that Iran holds responsible for an attack in the city of Ahvaz in southwestern Iran that killed 24 people.