* Novo Nordisk rejects ruling, weighing options
* Fine could amount to 15 percent of Russian sales - FAS (Adds details)
MOSCOW/COPENHAGEN, Sept 24 (Reuters) - Novo Nordisk, the world's biggest insulin maker, on Friday said it was considering its options after Russia's anti-monopoly service FAS on Friday ruled the Danish company breached competition law and threatened to impose a heavy fine.
"There's been a decision and we do not agree. We're undecided in what to do next but we're weighing our options," a company spokeswoman said.
According to a FAS official, Novo's Russian subsidiary had refused to sign direct contracts with most distributors.
"That influenced the price formation for important medicines, including insulin," the FAS website www.fas.gov.ru quoted Timofey Nizhegorodtsev, head of the FAS department which oversees social services and trade, as saying.
The FAS threatened to impose a fine which could amount to between 1 and 15 percent of Novo's Russian revenue.
Novo said it had not received any numbers from Russian authorities.
Novo Nordisk would not detail its Russian sales figures.
Shares in the company dropped to close at 532 Danish crowns in Copenhagen on Friday after trading at 534.5 before the news. (Reporting by Maria Plis and Peter Levring; Editing by David Cowell)