South Korea's Defence Ministry said Tuesday that senior members of its cyber warfare unit had been questioned over their possible involvement in a widening scandal over state interference in elections.
Areas of the unit's headquarters were searched and several of its commanders questioned, a ministry official said.
The main opposition Democratic Party (DP) has accused the unit of posting online comments prior to last year's presidential election, smearing opposition candidate Moon Jae-In and extolling his ruling party rival -- and eventual winner -- Park Geun-Hye.
Similar accusations against members of the National Intelligence Service (NIS) have already resulted in the arrest of the former head of the domestic spy agency.
The defence ministry has acknowledged that four members of the cyber unit had posted such comments, but insists they acted alone and not as part of any coordinated campaign.
The defense ministry set up the 400-member special unit in 2010 as part of efforts to expand the military's cyber warfare capability to counter hacking threats from North Korea.
The accusations of meddling by state agencies in the electoral process has been simmering away for months, but has gained traction in the past week, with a senior prosecutor investigating the affair saying his team had been pressured to go slow with the probe.