Denmark has recalled its ambassador from Tehran and called for fresh EU sanctions against Iran after its security services accused Iranian intelligence service of plotting an assassination on Danish soil.

The Danish intelligence chief, Finn Borch Andersen, said on Tuesday that the alleged murder plot had targeted the exiled leader of the Arab Struggle Movement for the Liberation of Ahvaz (ASMLA), a separatist group that has a history of carrying out attacks in Iran.

“We are dealing with an Iranian intelligence agency planning an attack on Danish soil. Obviously, we can’t and won’t accept that,” Andersen said.

A Norwegian national of Iranian background has been arrested in Sweden and since extradited to Denmark in connection with the foiled attack, according to officials.

The announcement came as Tehran scrambled to muster European support before the US re-imposes stringent sanctions on the country early next month. The European Union, Iran, China and Russia have set out a plan to sidestep those unilateral US sanctions.

Iran’s foreign ministry spokesman, Bahram Qassemi, dismissed the allegation and said that the timing of the accusations was suspicious. “This is a continuation of enemies’ plots to damage Iranian relations with Europe at this critical time,” he said, according to the semi-official Tasnim news agency.

Andersen revealed on Tuesday that a massive police operation that cut off Copenhagen from the rest of Denmark for several hours last month was triggered when police noticed a stolen, Swedish-registered car near the home of an Iranian opposition activist.

Fearing that an attack was imminent, Danish authorities closed the Øresund bridge linking Denmark and Sweden and the Great Belt bridge between the islands of Zealand and Funen. Hundreds of Danish police and soldiers used cars, sniffer dogs and helicopters to hunt for the rental car.

The incident came shortly after Tehran summoned UK, Dutch and Danish envoys and urged Denmark and the Netherlands to extradite Iranian exiles who they said were responsible for a terrorist attack on September 23 in the Iranian city of Ahvaz, which killed at least 24 people, including children. The ASMLA initially took responsibility for the attack, but later withdrew its claim.

The Danish foreign minister, Anders Samuelsen, said the foiled attack was “completely unacceptable” and that his government “will respond to Iran and is speaking with European partners on further measures”.

France has also recently accused Iran of plotting attacks on European soil. In October, French diplomatic sources said that they had concluded that Iran’s ministry of intelligence was behind a foiled bombing attack that targeted a rally organised by an Iranian opposition group near Paris in June.

An Iranian diplomat was among six people who were arrested for allegedly plotting the bombing of the event, which featured among its guests senior US politicians including Rudy Giuliani, Donald Trump’s attorney.

Tehran denied the allegations, which it called a conspiracy to “sabotage Iran’s ancient and longstanding relations with France and other significant European countries”.

In May, the US secretary of state, Mike Pompeo, claimed that Iran’s Revolutionary Guard was carrying out “assassination operations in the heart of Europe”, an allegation that at the time bewildered security experts, given that there had been no recent killings in Europe officially attributed to the Iranian state. Since then, France and now Denmark have directly blamed Tehran.

The most recent killing of an Iranian dissident took place in The Hague in November last year, when a gunman shot Ahmad Mola Nissi, who was also a former leader of a group closely linked to the ASMLA, which had claimed responsibility for several attacks in Iran.

Relations with Europe are vital to Iran’s bid to weather out US-imposed sanctions. Unlike the US, which has withdrawn from the 2015 nuclear deal, the EU has remained adamant that it wants to preserve the deal. Trump’s first set of sanctions – hitting the country’s access to dollars, gold and precious metals – were reimposed in August.

They are to be followed by a set of even more stringent measures by 4 November, including an embargo on the imports of Iranian oil and sanctions on its banking sector.