Some 30,000 Catholics gathered at the city's central cathedral square for a mass honouring Archbishop Teofilius Matulioni.
Some 30,000 Catholics gathered at the city's central cathedral square for a mass honouring Archbishop Teofilius Matulioni, who was officially recognised as a martyr in December by Pope Francis.
Lithuania's Soviet-era rulers repeatedly sent him to prisons and labour camps for standing up to the atheist regime.
Addressing the crowd, Vatican representative Cardinal Angelo Amato hailed Matulionis's "heroism" under "ruthless dictatorships which strove to annihilate the Church."
"Torture did not bend his will. He did not give in to hatred," Amato said.
Those gathered, including pilgrims from neighbouring Russia, Poland, Belarus and Latvia, cheered as a huge painting showing Matulionis dressed in prison garb was unveiled.
Lithuanian President Dalia Grybauskaite, who attended Sunday's beatification mass, said Matulionis remained steadfast in his commitment to the truth during his many years behind bars.
Nearly 2,000 kilometres away, Pope Francis congratulated Lithuanians during Sunday Mass at St. Peter's Square.
In order for him to be canonised as a saint, the Vatican will have to attribute a miracle to the beatified Matulionis.
The Soviet regime imprisoned him for a decade in 1946 after he refused to condemn armed Lithuanian resistance against Moscow's rule and criticised its repression of Catholics.
He was eventually released and managed to keep secretly in contact with the Vatican from behind the Iron Curtain despite being spied on for years.
He died in 1962 in Soviet-occupied Lithuania at the age of 89 under mysterious circumstances.
There is widespread suspicion that he was injected with poison by a nurse on orders of the Soviet KGB secret police.
The Soviet Union annexed Lithuania and fellow Baltic states Latvia and Estonia during World War II under a deal with Nazi Germany.
Mass deportations to Siberia and Central Asia followed.
In 1990, after three years of peaceful protest, Lithuania was the first republic to break free from the Soviet Union.
It joined the European Union in 2004.
Three quarters of Lithuania's 2.8 million people identify as Roman Catholic.