* Fine equals 3 pct of firms' combined 2010 turnover
* Says oil firms had understanding to withdraw a type of fuel
Jan 10 (Reuters) - Romania's competition watchdog levied fines totalling 880 million lei ($257 million) on oil companies including the country's largest firm Petrom for breaking anti-trust rules, the agency's director said on Tuesday.
The watchdog also fined local units of OMV (Petrom's owner) and Rompetrol Downstream, along with MOL , Lukoil and ENI, for having an understanding to withdraw a certain type of fuel from the market in 2008.
The fines amount to roughly 3 percent of the companies' combined turnover in 2010, competition watchdog director Bogdan Chiritoiu said.
"It is by far the largest sanction handed out by the Competition Council and it is ... tied to direct evidence of an understanding between companies," Chiritoiu told a news conference.
Petrom officials said they would issue a reaction to the decision later on Tuesday.
By 1130 GMT, Petrom shares traded 0.5 percent down at 0.2950, slightly weaker than the blue-chip index. ($1 = 3.4237 Romanian lei) (Reporting by Luiza Ilie; Editing by David Holmes)