THE HAGUE, Netherlands >> Ukrainian President Volodymyr Zelenskyy was in the Netherlands on Thursday for a surprise visit to the city that is home to the International Criminal Court, which has issued an arrest warrant for Russian President Vladimir Putin.

Zelenskyy’s visit to The Hague, which calls itself the international city of peace and justice and hosts the ICC and the United Nations’ top judicial organ, the International Court of Justice, came a day after he denied that Ukrainian forces were responsible for what the Kremlin called an attempt to assassinate Putin in a drone attack.

On a visit to Helsinki on Wednesday, Zelenskyy told reporters: “We didn’t attack Putin. We leave it to (the) tribunal.”

The ICC said in a March 18 statement that Putin “is allegedly responsible for the war crime of unlawful deportation of (children) and that of unlawful transfer of (children) from occupied areas of Ukraine to the Russian Federation.”

But the prospect of Putin being sent to The Hague is a remote one as the court does not have a police force to execute warrants and the Russian president is unlikely to travel to any of the ICC’s 123 member states that are under an obligation to arrest him if they can.

ICC Prosecutor Karim Khan has made repeated visits to Ukraine and is setting up an office in Kyiv to facilitate his ongoing investigations in the country.

However, the ICC does not have jurisdiction to prosecute Putin for the crime of aggression — the unlawful invasion of another sovereign country. The Dutch government has offered to host a court that could be established to prosecute the crime of aggression and an office is being established to gather evidence.

The new International Center for Prosecution of the Crime of Aggression should be operational by summer, the European Union’s judicial cooperation agency, Eurojust, said in February.

Zelenskyy’s visit to The Hague came as questions continued to swirl around Russia’s claim that it foiled an attack by Ukrainian drones on the Kremlin early Wednesday. Moscow branded it an unsuccessful assassination attempt against Putin and promised retaliation for what it termed a “terrorist” act.

Air raid sirens went off in Kyiv overnight, but there were no immediate reports of any airstrikes on the Ukrainian capital.

Putin wasn’t in the Kremlin at the time and was at his Novo-Ogaryovo residence outside Moscow, his spokesman Dmitry Peskov told Russia’s state news agency RIA Novosti.

There was no independent verification of the purported attack, which Russia authorities said occurred overnight but presented no evidence to support it. Questions also arose as to why it took the Kremlin hours to report the incident and why videos of it also surfaced later in the day.

White House press secretary Karine Jean-Pierre said the U.S. was “unable to confirm the authenticity” of Russia’s claims of a Ukrainian attack on Moscow. Asked whether the U.S. believed Putin was a lawful target of any potential Ukrainian strike, Jean-Pierre said that since the start of the conflict, the U.S. was “not encouraging or enabling Ukraine to strike beyond its border.”

Asked whether the U.S. was concerned that the accusation might have been a false flag operation by Russia to serve as a pretext for more aggressive military action on Ukraine, Jean-Pierre said she didn’t want to speculate, but added, “Obviously Russia has a history of doing things like this.”

The Netherlands has been a strong supporter of the Ukrainian war effort since Russia’s invasion last year. Among military equipment Prime Minister Mark Rutte’s government has promised are 14 modern Leopard 2 tanks it is buying together with Denmark. They are expected to be delivered next year. The Netherlands also joined forces with Germany and Denmark to buy at least 100 older Leopard 1 tanks for Ukraine.

Among other military hardware, it also sent two Patriot air defense missile systems and promised two naval minehunter ships as well as sending military forensic experts to assist war crime investigations. Zelenskyy’s visit came on the day the Dutch remember their war dead.