Reuters television footage showed players arriving for the session which began at 1730 local time (1530 GMT) and Messi did not appear.
Unhappy Lionel Messi missed Barcelona's first training session of the new season on Monday, days after his shock announcement that he wants to leave the only club he has played for professionally.
Messi's failure to show up for the session, the first under new Barcelona coach Ronald Koeman, was widely expected after the 33-year-old Argentine also failed to show up for a pre-season medical on Sunday.
Reuters television footage showed players arriving for the session which began at 1730 local time (1530 GMT) and Messi did not appear.
The six-times world player of the year insists he has a clause in his contract that allows him to leave on a free transfer -- a claim disputed by Barcelona and La Liga.
Messi's lawyers plan to invoke a clause in his four-year contract, signed in 2017, which would have allowed the forward to leave the club for free if he had requested it by June 10.
They will argue that date -- nominally the end of the season -- is now irrelevant after the coronavirus pandemic forced an extension of the La Liga season deep into August.
However, La Liga said on Sunday that the only way a club can sign the Argentine forward is if he triggers a release clause of 700 million euros ($836 million).
Messi's decision came after Barcelona failed to win any silverware last season, which finished with a humiliating 8-2 defeat to Bayern Munich in the Champions League quarter-finals.
Supporters who waited outside the training ground on Monday were split over Messi's decision.
"I really want Messi to stay," Brazilian Fabio Alfredo Suarez told Reuters.
"Messi lives in my heart -- it's a pity that he leaves, I wanted him to leave through the front door of the club.”
Spaniard Ivan Antolin Beltran remembered that Barca had helped Messi through the earlier stages of his career.
"After all that Barca has given to Messi throughout his career, which started here as a child... they paid him for all his medicines and everything ... I think his way of behaving is a bit incorrect," he said.
