MOSCOW, December 9 (RIA Novosti) - The acting leader of the Russian Orthodox Church gave a tribute to the late Patriarch Alexy II on Tuesday at a funeral service in Moscow, praising his achievements in reviving the Church since communism.

"Today his Holiness, standing before the face of God, can say that he left us with a different Church: no longer powerless and weak," Metropolitan Kirill of Smolensk and Kaliningrad said during the liturgy at the Cathedral of Christ the Savior.

"The Church is with its people... Millions of people have realized that without God and his truth, there can be no human truth," he said.

Alexy II died of heart failure at the age of 79 on Friday. He became patriarch in 1990, a year before the Soviet Union's collapse, and presided over the rebuilding of thousands of churches and monasteries and the construction of hundreds of new churches across the country.

The liturgy, which began at 9:00 a.m. (06:00 GMT) was attended by Russian President Dmitry Medvedev and Prime Minister Vladimir Putin, along with the heads of state and religious leaders several Orthodox former Soviet states.

After the service, the patriarch's body will be taken across town to the Epiphany Cathedral, where he will be buried.

Kirill, 62, was appointed interim leader of the Russian Orthodox Church on Saturday, the day after Alexy II died of heart failure at the age of 79. He is considered a likely candidate to replace the patriarch when Church's national council convenes within the next six months to elect a new leader.

Thousands of people have been gathered outside the Cathedral of Christ the Savior since early morning to pay their respects to the patriarch. The cathedral had been demolished under Joseph Stalin and was rebuilt during the 1990s.

People attempting to reach the cathedral by car have brought traffic to a standstill throughout much of the city center, prompting traffic police to issue a request that drivers avoid using their vehicles until late afternoon.