Half a lifetime ago, artist Yoko Ono lay in an Amsterdam hotel bed with her husband, John Lennon, staging a week-long "bed-in" for peace.

The couple said they felt very alone in their activism.

Today, Ono, whose energy for campaigning has never tired, sees a world full of an activism that maintains her energy and faith in humanity.

"When John and I did the bed-in, not many people were with us. But now there are so many activists; I don't know anyone who is not an activist," she said in Berlin yesterday on her 80th birthday.

The bed-in protest by the late Beatle and Ono in 1969, against the Vietnam War, was repeated in Montreal, Canada. Press attention was huge but much of it was mocking.

Ono, gave a sell-out concert in Berlin on Sunday with her son, Sean Lennon. It closed with the anthem "Give peace a chance".

Ono said it was still crucial that people "stand up for peace".

The artist, born to a wealthy Japanese family in Tokyo in 1933, is now a passionate opponent of fracking, a technology that has sharply lifted energy output in the US but which critics fear pollutes water deep underground and increases the risk of an earthquake .

"Fracking is an incredible risk to the human race, I don't know why they even thought of doing it," she said.

Ono, whose birthday is being marked by a major retrospective of her work in Frankfurt, Germany, said she feels that she is becoming freer in her art.

"My attitude has changed . I'm allowing things to happen in a way I hadn't planned before," she said.

"I'm surprised that I'm 80 . Not everybody gets there."