The archbishop said he visited eastern Poland to celebrate the First Communion of a relative; he is now in Białystok.
Archbishop Kondrusiewicz wrote an email to Belarus' special border committee Sept. 1 asking for an explanation of his refused entry, and is awaiting a reply.
The archbishop has spoken in defense of protests following last month's presidential election.
He demanded an investigation last week into reports that riot police blocked the doors of a Catholic church in Minsk while clearing away protesters from a nearby square.
He met with Interior Minister Yuri Karaev Aug. 21 to express his concerns about the government's heavy-handed response to the protests.
He prayed outside a prison Aug. 19 where detained protesters were reported to have been tortured.
Protests have taken place across Belarus since the August election, and thousands of protesters have been detained. According to the BBC, at least four people have died in the unrest.
US Secretary of State Mike Pompeo has said the election "was not free and fair," citing "severe restrictions on ballot access for candidates, prohibition of local independent observers at polling stations, intimidation tactics employed against opposition candidates, and the detentions of peaceful protesters and journalists."
Electoral officials said that the opposition candidate, Sviatlana Tsikhanouskaya, earned 10% of the vote. She was detained for several hours after complaining to the electoral committee, and has fled to Lithuania.
Archbishop Kondrusiewicz told CNA that "at the present time, we are asking for prayer, not only for the Catholic Church, but for a peaceful solution for the situation in Belarus because I'm very much afraid of civil war. The situation is very, very difficult, very critical."
He expressed appreciation "to Catholics around the world for their solidarity, for their prayers, for their moral support in this very critical time for my nation."
(Story continues below)
Subscribe to our daily newsletter
Luke Coppen contributed to this report.