MOSCOW — Ukrainian and Russian officials spent the day Friday hammering out the details of a highly anticipated prisoner exchange, officials in Kiev and Moscow reported, as each country continued to explore how the newly installed administration of Ukrainian President Volodymyr Zelensky will reshape the hostility between the two neighbors.

Ukraine’s new chief prosecutor reported early in the morning that the large-scale exchange was underway, but Zelensky’s office said the report was premature, and the Ukrainian security service said there would be no swap on Friday.

More than 60 prisoners were reported to be involved, including 24 Ukrainian sailors who were detained when their ships were seized in 2018 in the Kerch Strait between Crimea and the Russian mainland.

Russian and Ukrainian news services reported that final negotiations were continuing and that both sides expect the exchange to happen. They have been in talks over such a move all summer.

Zelensky’s office was critical of the preliminary reports that the exchange was underway.

“It is not the first time we have seen such information chaos caused by some reference to unconfirmed information and multiple ‘sources.’ We urge everyone to understand the consequences of misinformation: it’s like playing on society’s emotions. When this reciprocal release of detained persons is completed, the Office of the President will announce that via official channels,” his office said on Facebook.

Valentin Rybin, a lawyer for Russians held prisoner by Ukraine, said that the Russian prisoners were preparing to leave but were still in detention and that Zelensky had yet to issue them pardons.

The most prominent prisoner expected to be released on either side was the filmmaker Oleg Sentsov, who was arrested by the Russians in Crimea in 2014 and sentenced to a 20-year term on a charge of plotting terrorism. Last year, he conducted a 145-day hunger strike, demanding the release of Ukrainian prisoners held by Russia. He was awarded the Sakharov Prize for Freedom of Thought by the European Parliament and has been supported by prominent filmmakers in Europe as well as in Russia.

A member of the Ukrainian parliament, Viktor Medvedchuk, visited two other Ukrainian prisoners at Moscow’s Lefortovo prison, taking them bread and salt in a symbolic welcome.

A Russian journalist with the Ria-Novosti news agency, Kirill Vyshinsky, was released on bail Wednesday by a Ukrainian court, though he has told reporters that he wants to stay in Ukraine to clear his name in the courts. Vyshinsky was arrested in May 2018 and charged with treason; he was still awaiting trial.

Russia seized Crimea from Ukraine in the spring of 2014after the Maidan protests in Kiev that led to the ouster of Ukrainian President Viktor Yanukovych. Shortly after, rebellion against the new government was launched in two regions in eastern Ukraine. Russia has played the leading role in fostering that rebellion, which has remained more or less at a stalemate for the past five years.

Zelensky, a comic actor whose most famous television role was as a schoolteacher whose viral rant propels him to the presidency, became president in fact this May, elected in April by a Ukrainian population that had grown weary of the war and of the deeply rooted corruption that is a feature of the nation. He said he wanted to find a way to ease tensions in the east but had only a vague platform. He won the election easily, and his backers took control of the parliament in voting this summer.

Zelensky’s new cabinet was installed Thursday.

The news of the release was first reported on Facebook by Ukrainian lawmaker Anna Islamova, in a post reshared by Ruslan Riaboshapka, Ukraine’s new prosecutor general.