Marseille dominated a dull Group F game, looking set to prevail, but they proved too clumsy, too slow, and eventually paid dearly for their lack of sharpness.
Cesar Azpilicueta, trying to catch Dmitri Kombarov, deflected the Russian's cross into his own net with nine minutes left.
"It's the worst scenario," OM coach Didier Deschamps told reporters. "We played Russian roulette and we lost."
Marseille made an enthralling start with Lucho Gonzalez in a class of his own for a few minutes.
France winger Mathieu Valbuena looked off the pace, however, on the right flank with Andre Ayew, the son of Abedi Pele who scored two in Marseille's semi-final against Spartak in 1990/91, far from his best on the left.
The home side's best effort came on the stroke of halftime when Benoit Cheyrou had a fine volley parried away by Andriy Dykan.
The visitors, however, gained confidence after the break.
Marseille keeper Steve Mandanda pulled off a cracking save on the hour, stretching his right arm to parry Ibson's header from close range.
Deschamps's team finally upped the pace as France striker Andre-Pierre Gignac replaced Brandao in the 62nd minute.
A transformed Valbuena unleashed a fine volley on the turn only for Dykan to block the diminutive midfielder's attempt.
"I don't think we played a bad game. At the end of last season, everything was going our way," midfielder Benoit Cheyrou told reporters. "It's not the case any more. We score an own goal, we hit the post."
Gignac hit the post with a 20-metre strike two minutes into stoppage time.
Marseille, however, had it coming, Deschamps suggested.
"That's football. If you dominate without scoring, you can always concede a goal because of a mistake or because of a deflected cross," the 1998 world champion said.
Marseille are now facing a tough challenge if they are to advance from a group featuring Chelsea, whom they visit in two weeks time.
"I think our real rival in this group is Spartak so clearly we got off to the worst possible start," said Deschamps.
"We will probably need to win in Moscow (on November 23) in different conditions, when the temperatures will be much lower."
'I don’t know why the Ballon d'Or was cancelled. Maybe some years later I’ll understand what the reason was. For now, I don’t have the answer': Robert Lewandowski reflects on missing out on prestigious award in 2020
Liverpool star issues 'I'm not leaving' statement after being linked with move away from Anfield
