Rijeka sporting director Ivan Mance has confirmed that Chelsea have made an official bid for Andrej Kramaric.
The 23-year-old, who has also been linked with Leicester City, has scored an impressive 21 goals in just 19 league games this season.
The Blues are believed to have launched a bid in the region of £8m and are confident of completing a deal when the January window officially opens.
"I can confirm that our office has received a formal offer from Chelsea," Mance told Sportske.
Kramaic, who has scored twice in four appearances for Croatia, has netted 55 goals in 65 appearances for Rijeka, who he joined from Dinamo Zagreb in 2013.