West Ham and Rapid Vienna fans clashed in ugly scenes inside the London Stadium during their Europa League tie on Thursday.
Police and stewards had to form a barrier between both sets of supporters in one corner of the ground as objects were thrown across the divide.
One fan could be seen in footage launching a large object into the melee while others chucked water bottles as officers and staff attempted to restore order.
The row had been sparked after West Ham's Declan Rice fired his side in front after 29 minutes.
Rapid Vienna fans reportedly stormed the home end to confront West Ham supporters before chaos ensued.
Declan Rice's goal sent the crowd into a frenzy before brief chaos ensued ( Image:
AFP via Getty Images)
It is West Ham's first home fixture in Europe since 2016, and the club marked the occasion with a light show prior to kick-off.
Some objects are believed to have been thrown while the stadium floodlights were dimmed during the show.
Rice's goal then sent the home crowd into jubilation, getting them off to a superb start when he finished off Michail Antonio's cross.
But officers and stewards had to remain in position out of fear of trouble erupting again after missiles were exchanged.
Fortunately there were no more clashes during the match as the Hammers eventually ran out 2-0 winners.
Said Benrahma scored a well-taken placed finish in the dying minutes to wrap up the victory and the three points as West Ham maintained their perfect start in the competition.
There were more altercations in the Europa League in France as fans of Marseille and Galatasaray clashed before kick-off and during the game.
Flares were thrown between supporters before riot police had to be called.
At one stage the match was even temporarily suspended in the 37th minute until the situation had calmed after captains of both teams got involved and liaised with their own fans.
Elsewhere in the Europa League, Leicester City were beaten 1-0 away at Legia Warsaw following Mahir Emreli's first-half goal.
Rangers were also downed by the same scoreline against Sparta Prague as more unsavoury scenes marred the contest.
Celtic were also on the losing side as they suffered a heavy 4-0 defeat at the hands of Bayer Leverkusen.