German police have designated the Europa League match between Union Berlin and Malmö on Thursday as high risk after trouble between fans at last week's game in Sweden.
Police said communications by fan groups are being monitored and concrete plans on the deployment of officers will only be decided on the day of the match.
"There will be a very large police presence," confirmed Union communications director Christian Arbeit at a news conference on Wednesday. The number of stewards provided by the club at the stadium will be increased by 100 to 400, he added.
Union won 1-0 last Thursday in the away group game when spectators in both fan blocks set off massive pyrotechnics. The match was close to being abandoned and the European football federation UEFA is investigating.
Malmö fans are closely associated with supporters of Hertha Berlin, Union's city rivals. They are only allowed in Union's Stadion An der Alten Försterei with Swedish identity cards, with 1,150 visiting tickets sold.
Union coach Urs Fischer wanted to concentrate on football during his news conference.
"It's about sending the best possible team onto the field," he said.
Union's fellow Bundesliga side Cologne is not allowed spectators at Thursday's Conference League game at Partizan Belgrade due to a separate UEFA ruling following disturbances at last month's match at French side Nice.
Union have also been criticized in Germany and by their own fans for allowing Hungarian nationalist Prime Minister Viktor Orban to visit the club this week. He met with Union's Hungary midfielder Andras Schäfer.
"There was an official letter from the Hungarian embassy asking us to allow a private meeting of a Hungarian national player. We complied with this request. We did not officially receive him," Arbeit said.
