Jazz legend Al Jarreau has been admitted in a "critical" condition to a French hospital after falling ill just before he was due to go on stage, health officials said.

Jarreau, 70, who has won seven Grammy awards, was about to begin a festival concert late Thursday in the southern Alpine town of Barcelonette when he was taken ill with an unduly rapid heart beat, they said.

He was treated on the spot for a couple of hours but was later flown by helicopter to a hospital intensive care unit in nearby Gap where he was admitted with respiratory problems, the hospital said in a statement.

"Doctors are concerned about his condition," it said. "He is being given appropriate treatment and they hope to see an improvement in the coming hours."

Jarreau's French trip was part of a tour scheduled to take him to Germany, Austria and Azerbaijan, and he was due to give concerts in the United States and Japan in the coming months, according to his website.

The veteran has staged two concerts in the Bulgarian capital Sofia - in the summer of 2006 and 2007, bringing here his high-quality music, imaginative improvisation and radiant smile.

The second time the Bulgarian jazz fans were treated to a double portion of pleasure as Jarreau came together with guitarist-singer George Benson. Bulgaria was the only Eastern European country, where the two jazz stars presented their best- selling CD, "Givin' It Up," with cameo appearances by Jill Scott, Patti Austin and Paul McCartney, and two Grammy Awards.

The American jazz musician holds Grammy awards in three different categories, including jazz, pop and rhythm and blues. He features among the most influential contemporary musicians, becoming a legend with his remarkable alternation of jazz and soul vocal standards.