Moscow is influencing various religious institutions in Europe, Selensky said at a press conference in Kiev on Tuesday evening.
Ukraine must therefore constantly publicise the true facts, the president added.
As soon as one is negligent in one's own information work, "everything is filled with information from Russia".
It is important not to lose contact with the Vatican, Italy, the whole of Europe and the United States.
Pope insists on religious freedom
Pope Francis expressed his concern about religious freedom in Ukraine on Sunday. He referred to a law signed by Zelenskyi: it is directed against the Ukrainian Orthodox Church (UOK), which is considered to be close to Moscow, and enables religious organisations linked to Russia to be banned by the courts.
Francis said that praying is not a crime. Every person who wants to pray should be allowed to pray in the church they consider to be their own.
"Please, no Christian church should be directly or indirectly banned," the Pope continued: "Churches are sacrosanct!"
Selenskyj now commented on this when asked, but did not go into the content of Francis' criticism.
At the weekend, the head of state emphasised that the law protects "Ukrainian Orthodoxy from dependence on Moscow and guarantees the dignity of the sanctuaries of our Ukrainian people".
The controversial law gives an authority the right to apply to the court to ban a particular religious community or organisation because of its links to Russia.
Ban plans due to espionage cases
The Ukrainian Orthodox Church (UOK) is not mentioned by name in the law.
However, MPs openly state that the aim of their proposal is to ban the UOC if it does not completely separate itself from the Orthodox Moscow Patriarchate.
The background: around two dozen of the church's clergy have been convicted of spying for the Russian secret service or justifying Russia's war of aggression since 2022.
Further trials are ongoing.
The Ukrainian government supports the Orthodox Church of Ukraine (OKU), which competes with the UOK.
It was founded in December 2018 with the help of the Ecumenical Patriarch Bartholomew I.
In recent surveys, significantly more Ukrainians declared their allegiance to this church than to the UOK.