Tenor Joseph Calleja and and Soprano Anna Netrebko have bowed out of a tour of Japan, citing fears of radiation from the Fukushima nuclear plant, the BBC has reported.

It said the two stars of New York's Metropolitan Opera had bowed out at the last minute despite assurances they would be safe.

In a statement, the Met said it had been forced to "scramble" to find replacement stars. It had brought in an expert on radiation to reassure members of the company about safety.

But Russian-born Netrebko remained unconvinced, the Met attributing her decision to "the emotional weight of having also lived through the tragedy of Chernobyl"

Peter Gelb Met general manager, said: "She didn't feel that she would be able to present her best performances and didn't want to disappoint her Japanese fans."  

Calleja, the Met said , "also had last-minute misgivings about performing in Japan at this time."

Tenors Marcelo Alvarez, Rolando Villazon and Alexey Dolgov will replace Calleja and Germany's Jonas Kauffmann, who withdrew from the tour last month.

"If there were a rationality clause in opera singers' contracts, not many opera singers would perform."

The Vienna Boys Choir, the Lyon Orchestra and the Stuttgart Chamber Orchestra are among several organisations to have cancelled concerts in Japan in the wake of the disaster.

Yet not all artists have stayed away. Last month opera giant Placido Domingo performed in Japan, later donating $200,000 (£121,000) to relief efforts.

Calleja will be in Malta next month for his much-expected concert on the Granaries.