German artist Otto Piene, known for his colourful paintings and gigantic open-air sculptures, has died at the age of 86.

He died yesterday, shortly after the opening of an exhibition of his work at Berlin's Neue Nationalgalerie.

His death was confirmed today by Markus Farr, a spokesman for the group Friends of the Neue Nationalgalerie, which organised the exhibition.

Piene was born in 1928 in Bad Laasphe, studying in Munich and Dusseldorf.

Together with fellow artist Heinz Mack, he founded the influential European post-war movement Group Zero in 1957.

In 1974 he was appointed director of the Massachusetts Institute of Technology's Centre for Advanced Visual Studies, retiring in 1993.

His work has been exhibited in more than 100 galleries and museums worldwide and was shown at the 1972 Munich Olympic Games.