Ograi BidCo said in a statement it was now offering 8.50 crowns in cash for each Opus share, up from its initial bid of 7.75 crowns, and representing a 42% premium compared to Opus' closing price on November 29, the day before the first bid.
Opus' share closed at 7.82 crowns on Thursday.
The Opus board said in a statement it unanimously recommended shareholders accept the offer, saying it was fair from a "short-term financial perspective", although not recflecting "the full long-term fundamental value of Opus".
"We believe this revised offer is highly compelling for Opus' shareholders," Searchlight Founding Partner Oliver Haarmann said in a statement.
The acceptance period in the offer runs to January 13, 2020.
Opus also said its fourth-quarter core profit (EBITA) would be lower than current market expectations as "continued growth activities" would temporarily affect earnings.
(Reporting by Johannes Hellstrom; Editing by Simon Johnson)