Veteran Sao Paulo midfielder Oscar has been hospitalized due to a heart condition, the Brazilian Serie A club said on Tuesday.

In this undated photo, Shanghai SIPG FC player Oscar reacts in a football match in Shanghai. (PHOTO / XINHUA)

The 34-year-old collapsed during an interval test on an exercise bike at the Barra Funda training centre, part of his recovery from a calf injury.

He was taken by ambulance to the Albert Einstein hospital, where he remains in a stable condition and under observation as doctors conduct further tests.

"In accordance with standard procedure and respecting the player's privacy, new information will be released as soon as updates are available from the medical team, in agreement with Oscar," Sao Paulo said.

Oscar joined Sao Paulo on a three-year deal last December, returning to his original club after successful spells with Shanghai Port and Chelsea.

Injuries, including a lumbar fracture sustained in July, have limited the former Brazil international to 21 matches across all competitions this year.

Local media reported that his latest setback has prompted the playmaker to consider retirement.