Veteran French rocker Johnny Hallyday is back in hospital in Los Angeles after a health scare in the Caribbean and is due to be released on Friday, his manager said.

"He has been undergoing medical examinations since Tuesday but he only slept last night," Sebastien Farran said in a text message.

"The nature of the examinations is general," he told AFP on Thursday.

The 69-year-old singer was treated for bronchitis in August at a hospital in the French Caribbean island of Martinique. He had been flown there by helicopter after falling ill on nearby Saint Barts island, where he also has a residence.

The rocker has sold more than 100 million albums and played 45 major tours in a career that began in the 1960s. He is currently in the middle of another major tour.

Hallyday sent a reassuring tweet to fans on Thursday saying he would return to the studio on Monday to record a song that will be a duet with Canadian diva Celine Dion.

Farran backed this saying recording for the new album "is scheduled to resume next week."