Saudi Arabia's market regulator fined contractor Mohammed Al Mojil Group (MMG) and sentenced two of its executives to five years in prison for breaching rules relating to accumulated losses, the firm said on Friday.

The Capital Market Authority's (CMA) Committee for the Resolution of Securities Disputes, which judges securities cases in Saudi Arabia, fined MMG SR1.6 billion ($427 million), a representative for the family said.

The committee also sentenced founder Mohammad Al Mojil and his son Adel Al Mojil, the firm's chairman, to five years in prison.

MMG has not traded on the Saudi bourse since July 2012, when the CMA suspended it shares over the losses after it over-extended itself trying to take advantage of a construction boom in the kingdom.

Neither the CMA nor the judicial committee were immediately available for comment.

In an emailed statement, the Mojil family denied wrongdoing and said they would appeal the decision, calling the investigative process "defective from the start".

"There has been a fundamental and deliberate lack of due process throughout," the family said.

They allege the men were not given an opportunity to respond to certain evidences used against them.-Reuters