LIVERPOOL (REUTERS).- John Lennon's son Julian and first wife Cynthia unveiled a monument to the late singer Saturday, the 70th anniversary of his birth, and said the time for mourning the former Beatle was over.

The presentation of a $350,000 18-foot structure, designed to promote peace, was one of several events being held around the world to celebrate one of pop music's most influential singers and songwriters who was murdered in New York in 1980 at the age of 40.

Internet search site Google paid tribute to Lennon with a hand-drawn logo and mini-video based on his hit "Imagine."

Manhattan planned a benefit concert and Lennon's widow Yoko Ono was to perform alongside their son Sean as the Plastic Ono Band in Reykjavik.

Cynthia, 71, and Julian Lennon, 47, looked on in Lennon's birthplace Liverpool as a choir performed his music. A crowd of several hundred people gathered in Chavasse Park for the event.

"I think the mourning is over for John," said Cynthia, who was married to Lennon between 1962 and 1968. "I think it's time to celebrate, which is what we're doing."

Musician Julian added: "I think most things have been said. We come here with our hearts to honor dad and to pray for peace and say thank you to each and every one of you and everyone involved in the celebrations today."

As one half of the songwriting partnership in the Beatles alongside Paul McCartney, Lennon was responsible for much of the band's catalog, including seminal hits like "She Loves You," "I Want to Hold Your Hand" and "A Hard Day's Night."

The band is widely credited as being the most successful in pop history, and Lennon went on to make his mark as a solo artist after the group split in 1970 with classic songs including "Imagine."

Ono said his influence continued to be felt, 30 years after his death.

"It's very interesting, you know, that songs like 'Gimme Some Truth' mean a lot now, and of course 'Give Peace a Chance' ... 'Imagine'," she said in Reykjavik Friday.

"All his political songs really have a lot of meaning right now for people," she said.

Lennon remains big business, and the anniversary, just months before the 30th anniversary of his death, has seen the release of a new wave of Lennon-related merchandise and music.

Ono oversaw the making of a digitally remastered Lennon catalog that includes eight studio albums and several newly compiled titles on the EMI Music label.

(Reporting and writing by Mike Collett-White; Editing by Janet Lawrence)