Madonna honoured Michael Jackson during her London concert at the O2 Arena, where the late singer was due to stage his much-awaited comeback.

The Queen of Pop hailed the late King of Pop, describing him as one of the greatest performers the world has seen.

A huge picture of Jackson as a child was displayed above the stage as the `Material Girl' hitmaker carried out a short dance melody dedicated to the late star.

One of her dancers, clothed in Jackson''s trademark black hat, wooed fans with a moonwalk across the stage.

Jackson''s greatest hits, Billie Jean and Wanna Be Startin'' Somethin, were also performed in short versions.

"To one of the greatest performers the world has ever known - Michael Jackson," the Daily Star quoted Madonna as saying.

Jackson had been due to kick-start his This Is It tour at the same venue this month.

He died aged 50 on June 25 after suffering an apparent cardiac arrest allegedly triggered by an overdose of prescription drugs.

Russian dignitaries are upset with Madonna over the use of foul language to promote an upcoming show in St. Petersburg.

The Material Girl addressed the Russian crowd by saying "It''s f**king great" at the beginning of an online audio teaser for her `Sticky and Sweet' concert in Palace Square, scheduled for August 2.

According to Contactmusic, members of the legislative assembly in St. Petersburg have addressed Governor Valentina Matvienko with a proposal to sue Madonna for her comments.

This is not the first time that Madonna''s Palace Square show has come under fire.

Many city officials fear that the concert could offend the moral and religious sensibilities of the citizens of St. Petersburg.

Mikhail Piotrovsky, the head of the city''s Heritage Museum, has asked Madonna not to swear during the show.