The ministry said it had informed military prosecutors there were "reasonable suspicions" about the legality of the procedure, saying it could harm national security. It didn't provide further details.
The government, scheduled to announce the winner Saturday, made its announcement late Friday.
The acquisition of four multirole corvettes has caused political friction with the ruling Social Democratic Party favoring an offer from Damen, a Dutch company.
Army Chief of Staff Nicolae Ciuca, however, reportedly considered the deal too expensive. According to reports, France's Naval Group made a cheaper offer.
Romania has committed to upgrading its armed forces and equipment in the next decade.
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