SEOUL, South Korea — The Defense Ministry in South Korea said Thursday that at least 11 officials at its cyberwarfare unit, created four years ago to fight North Korean propaganda, had spread 2,100 online political messages praising President Park Geun-hye and her party or attacking their domestic opponents ahead of her election a year ago.

Military investigators asked prosecutors to indict the officials on charges of violating a law that bans public servants from meddling in domestic politics, the chief investigator, Maj. Gen. Baek Nak-jong, said at a news conference. But he said that the cyberwarfare specialists’ actions did not amount to trying to influence the election, a far more serious crime. The general said the specialists had no such intention and had criticized opposition parties and their members merely to defend the prior conservative government’s policies. Ms. Park won the election by a margin of a million votes.

The opposition Democratic Party called the military investigation an outrageous whitewash intended to prevent political fallout against Ms. Park.

The Defense Ministry started an investigation two months ago after the opposition claimed that not only the country’s National Intelligence Service but also its military had conducted an aggressive online smear campaign to undermine the popularity of Ms. Park’s opponents to help her win the election.