Lukoil has been operating in Romania since 1998 and is one of Russia's largest private oil firms. Romanian prosecutors raided Lukoil's office near the city of Ploiesti in October 2014 as part of the investigation into money-laundering and tax evasion worth 230 million euros, according to Reuters. The company briefly shuttered a local refinery shortly after.
A Ploiesti appeals court said they were expanding their investigation to include the local head of Petrotel Lukoil S.A. alongside five other employees, including two Russian citizens, Reuters said, citing a local state press agency.
The assets seized earlier this week included accounts held with Dutch and British banks and Lukoil Europe Holdings Bvatrium Holland shares in the Romanian company, the report added.
"It is Lukoil's hope that any hindrances to the functioning of this backbone enterprise will be successfully avoided," the company said in its press release.
Lukoil's press office did not answer CNBC emails requesting comment.