The Hungarian Tax Authority's decision to have counter-terrorism forces swoop on two Ukrainian armoured vehicles transporting $US80 million ($A114 million) to Ukraine marks a dramatic escalation of tensions that have already resulted in Hungary blocking tens of billions of euros in European Union aid for Ukraine.
Ukrainian Foreign Minister Andrii Sybiha said on X that the people detained were employees of Oschadbank and accused Hungary of "taking hostages and stealing money".
"This is state terrorism and racketeering," he added, demanding their immediate release and asking the EU to "provide a clear qualification of Hungary's unlawful actions".
Video posted on the Hungarian government's Facebook account showed armed counter-terrorism officers jumping out of a van as the Ukrainian vehicles pulled into a service station, pointing their guns at the windscreen before handcuffing the people inside and forcing them to lie face down on the ground.
"The National Tax and Customs Administration (NAV) is pursuing criminal proceedings on suspicion of money laundering," the authority said in a statement.
"On March 5, 2026, it detained seven Ukrainian citizens, including a former Ukrainian intelligence service general, and two armoured cash-in-transit vehicles, which were transporting a total of $US40 million, 35 million euros and nine kilograms of gold from Austria to Ukraine."
The tax authority said it was working together with counter-terrorism forces.
Government spokesman Zoltan Kovacs said the seven detainees would be expelled from Hungary.
It was not immediately clear what would happen to the money they were transporting.
Ukraine's ambassador to Hungary, Sandor Fegyir, went to the Budapest headquarters of the Counter-Terrorism Centre to try and meet with the detained Ukrainians, two Reuters witnesses said.
The detainees' lawyer Lorant Horvath said he had been unable to contact them.
Ukraine's ambassador to Budapest, Sandor Fegyir, was also unable to meet the detainees.
"This is an outrageous procedure... (T)he embassy, and indeed the consular service, must in all cases be allowed access to the accused," Horvath told Reuters.
"Defence lawyers must also be allowed (access)."
Ukraine advised its citizens against travel to Hungary, saying it could not guarantee their safety amid what it called the "arbitrary actions" of Hungarian authorities.
Hungary and Slovakia accuse Ukraine of deliberately delaying the resumption of oil flows via the damaged Druzhba pipeline for political reasons.
Ukraine denies the charge, saying it needs time to repair the damage caused to energy infrastructure by a Russian drone strike on January 27.
Hungarian Prime Minister Viktor Orban, who faces a serious challenge to his 16-year rule in an election on April 12, has made the war in Ukraine a central plank of his campaign, saying the opposition would drag Hungary into the conflict.
Ukraine's Oschadbank said its employees had been engaged in a routine operation.
"Since the start of the full-scale invasion, foreign currency and bank metals have been transported exclusively by land," it said in a statement.
"Similar trips are carried out by Oschadbank's cash collection vehicles on a weekly basis."
