Berlin: Former Soviet leader Mikhail Gorbachev, whose "perestroika" and "glasnost" reforms helped pave the way for the fall of the Berlin Wall, has greeted crowds at the city's iconic former Checkpoint Charlie border crossing.

Germany kicked off celebrations on Friday marking 25 years since the fall of the wall, set to culminate in rock stars and freedom icons joining millions at an open-air party.

Mr Gorbachev, 83, who is revered in Berlin for having refrained from a bloody crackdown on protesters in 1989, understated his own role in history, saying: "I am proud I could contribute a little bit to the fact that we live like this today".

But the Nobel Prize winner also warned of new East-West tensions sparked by the Ukraine crisis, saying both sides must "get a grip on the tensions that have emerged recently".