The plot allegedly involved three Polish extremists and a German journalist with ties to the far-right Alternative für Deutschland (AfD) party, as well as to a number of Kremlin-friendly Russian news outlets.

Their alleged task was to carry out a “false flag” operation in western Ukraine: burn down a Hungarian cultural centre, and make it look as though Ukrainian nationalists were responsible. The main beneficiary of the ensuing recriminations would be Russia.

If this was the idea, the fire last February in the town of Uzhhorod had the desired effect. There were no casualties, but tensions were inflamed in the Ukrainian region, which has a sizeable ethnic Hungarian minority.

Hungarian authorities were quick to blame Ukrainian nationalists and the anger contributed to the increasingly fraught relationship between Budapest and Kiev over the past year, which has caused cracks in EU and Nato solidarity in support of Ukraine.

Now, a year later in a Kraków courtroom, new details of what happened in Uzhhorod last year have been emerging.

Michał Prokopowicz, a Polish far-right activist, told the court last week that he was paid €1,500 (£1,300) to organise the attack by Manuel Ochsenreiter, a German journalist with multiple links to Russia, who works as an adviser to AfD MP Markus Frohnmaier.

Prokopowicz told the court he hired two associates, who are standing trial with him, to carry out the attack: Tomasz Szymkowiak and Adrian Marglewski, who are charged with promoting fascism and endangering lives or property with fire. They are yet to give testimony and have not yet entered pleas.

Manuel Ochsenreiter denies allegations that he paid Polish far-right activists to burn down a Hungarian cultural centre in western Ukraine. Photograph: Vyacheslav Prokofyev/Getty Images

The men allegedly returned to Poland via Slovakia shortly after the fire at the cultural centre and were identified by Ukrainian authorities through images from security cameras. Prokopowicz reported the success of the mission to Ochsenreiter, he told the court.

Prokopowicz faces up to 12 years in prison for inciting terrorism when the case continues in March, but the Polish court has so far declined to charge Ochsenreiter, who denies involvement.

If Prokopowicz’s testimony is true, however, it raises the question: what or who prompted Ochsenreiter to set up the attack?

Ochsenreiter edits the far-right Zuerst! magazine, and become an adviser last September to Frohnmaier, who was elected to the Bundestag from the southern German state of Baden-Württemberg in 2017.

Attention, however, is likely to focus on the journalist’s numerous ties to Russia. He has been a regular guest on the Kremlin-backed news channel RT. Usually introduced simply as a “German journalist”, he would often agree with Kremlin talking points on the war in Ukraine or give a far-right viewpoint on tensions in Germany over migration. He has also travelled to the self-proclaimed Donetsk People’s Republic in east Ukraine, where he was an “observer” for elections the international community regarded as illegitimate.

He had a regular column on the website of Katehon, a thinktank run by Konstantin Malofeev, a Russian financier who has been accused of supporting the pro-Russia insurgency. Malofeev has denied accusations of funding the far right in Europe.

A spokeswoman for Malofeev said Ochsenreiter was never paid for his columns or for any other work by the Russian financier or structures controlled by him.

The Berlin prosecutors’ office said a preliminary investigation was under way against “an employee of a Bundestag parliamentarian”, but would not say whether this was Ochsenreiter. Earlier, German media reported that prosecutors had opened an investigation into the case.

The AfD declined to comment on the allegations or news of the preliminary investigation. Neither Ochsenreiter nor Frohnmaier’s office responded to requests for comment from the Guardian.

Frohnmaier wrote on Facebook last week that Ochsenreiter had denied the allegations. He later told German media that Ochsenreiter had resigned from his position after the allegations emerged.

Mateusz Piskorski, the leader of Zmiana, was detained by Polish authorities in 2016 on suspicion of espionage for foreign powers. Photograph: Alexander Shcherbak/TASS

The journalist also had longstanding links to the Polish far right. An undated photograph unearthed by Anton Shekhovtsov, who researches European far-right movements, shows Ochsenreiter together with Prokopowicz and Mateusz Piskorski, the leader of the pro-Russia Zmiana party.

Ochsenreiter and Piskorski were directors of the European Centre for Geopolitical Analysis, which specialises in organising Russia-backed election missions with the participation of far-right and far-left actors from across Europe, as well as publishing literature pushing the Kremlin line on a wide range of issues.

In May 2016, Piskorski was detained by Polish authorities on suspicion of espionage for foreign powers, including Russia and China. He was not charged for another two years, making him a cause célèbre for the European far right, which claims his arrest is politically motivated. He has been in detention for two years, but the case has not yet been brought to trial.

In east Ukraine, Russia has funnelled cash, weapons and occasionally troops across the border to support and control the separatist territories that split away from Ukrainian government control in 2014.

The fire in western Ukraine was much lower key. It would appear to fit a pattern of low-grade, low-cost and deniable cultivation of a number of European far-right activists by Russian intelligence or Kremlin-friendly figures. It also represents an escalation from mere cultivation.

West Berliners watch an East German soldier on patrol on the other side of the Berlin Wall in 1961. Photograph: Paul Schutzer/Time & Life Pictures/Getty Images

Shekhovtsov compared the fire to historical “false flag” cases, such as when the KGB and the Stasi used agents to paint swastikas in West Germany in the 1950s in an attempt to emphasise the country’s failure to break fully from Nazism.

He cautioned against drawing a direct link to the Kremlin, claiming that Ochsenreiter could be freelancing in the hope of impressing his contacts in Moscow. “He knew what kind of things can be rewarded by the Russians, and for this he would have been rewarded,” Shekhovtsov claimed.

As in many other cases across Europe, the claims would suggest that pro-Russia actors have seized on genuine grievances and attempted to exploit them.

Hungary’s prime minister, Viktor Orbán. Budapest was quick to blame to blame Ukrainian nationalists for the attack in Uzhhorod. Photograph: Bernadett Szabó/Reuters

The incident worsened already delicate relations between Ukraine and Viktor Orbán’s nationalist government in Hungary. Hungary has complained about a restrictive language law meant primarily to tackle the dominance of Russian in Ukraine, but which has also worried the Hungarian minority in the west of the country.

For months, Hungary has blocked Ukraine’s efforts to move closer to Nato owing to disagreements over the language issue. This is despite strong warnings from the US that the Hungarian policy was playing into the Kremlin’s hands.

In a post on Facebook, the Ukrainian foreign minister, Pavlo Klimkin, said the evidence emerging in court in Kraków showed “the complexity and scale of Russian hybrid methods”.

He said: “It’s time for Europe to think systemically of how they could counter Moscow, which is doing everything it wants in the territory of the free world.”