Russian Orthodox leader with Pope Francis in historic talks.

The meeting is the first between a Pope and a Russian Church head since the Western and Eastern branches of Christianity split in the 11th Century.

The Russian Orthodox Church said the "persecution of Christians" in the Middle East and North Africa would be the central theme of the talks.

The two leaders are also expected to sign a joint declaration.

They embraced and kissed each other when they met at Havana airport.

"I'm happy to greet you, dear brother," Patriarch Kirill said.

"Finally," the Pope said.

The talks are being held during Pope Francis's stop-over on his way to Mexico. Meanwhile, Patriarch Kirill is visiting Cuba, Brazil and Paraguay.

The two leaders are now meeting behind the closed doors.

In the swirl of black - Vatican officials and security - a lone figure in white on the heated tarmac of Havana airport - Pope Francis arrived to do his part in healing one of the longest religious disputes.

In the airport was Russian Patriarch Kirill who arrived shortly before.

The venue is a compromise - after no contact in over five centuries, it would be impossible to have the first such meeting in the Vatican or Moscow, and Catholic Cuba is still in the Russian sphere of influence.

Back home the Patriarch has to overcome the anger of conservatives who still consider Catholicism a deviation from true Christianity. Clearly, this is a criticism he feels safe to ignore now.

Minutes later, the Pope and the black-robed Patriarch were holding each other by the shoulders and smiling warmly.

"Finally," said the pope in Spanish. The other first words of such greeting were drowned in the noise of cameras.

Then the leaders of Catholics and Russian Orthodox Christians sat down. It was almost business as usual, a top-level meeting.

In purely symbolic terms, this is an extraordinary moment, but it is perhaps even more significant in terms of church diplomacy, and the effort to warm relations within the Christian faith, the BBC's Will Grant in Havana says.

Patriarch Kirill has been the head of the Russian Orthodox Church since February 2009, while Pope Francis took up his role in March 2013.

The Roman Catholic Church has more than a billion members worldwide, while the Russian Orthodox Church numbers about 165 million.

The Russian Church is the largest and most powerful in the Orthodoxy faith, which is made up of a number of separate churches.

However, the encounter in Havana is not expected to lead to any immediate rapprochement between the Eastern and Western Churches.

Ahead of the meeting, the foreign policy chief of the Russian Orthodox Church, Metropolitan Illarion, said here were still differences between the two churches, in particular on western Ukraine.

One particular issue is the Ukrainian Greek Catholic Church, which follows eastern church rites but answers to the Holy See.

The Russian Orthodox Church has considered western Ukraine its traditional territory, resenting papal influence there.