SEOUL - A simmering row over alleged election meddling by South Korea's domestic spy service is threatening to boil over into a full-blown scandal that could seriously scald President Park Geun-Hye's administration.
An investigation into what initially seemed the work of a couple of maverick National Intelligence Service (NIS) agents, has now become a wider probe into a possibly coordinated online smear campaign against the opposition candidate in last year's presidential poll.
In the latest development, federal investigators on Tuesday questioned senior commanders at the Defence Ministry's cyber warfare headquarters over possible military involvement.
The probe has focused on the origin of multiple online posts that denounced opposition presidential candidate Moon Jae-In as a North Korean sympathiser, while extolling the virtues of ruling party candidate Park Geun-Hye.
Park, who won the election by a narrow margin, has strenuously denied any involvement.
Her opinion poll ratings remain high and analysts say there is currently no real threat to her legitimacy, unless she becomes implicated in any attempted cover-up.
In a recent meeting with opposition leaders over the issue, a clearly frustrated Park reportedly asked: "Are you seriously suggesting I was elected because of some online postings?"
But allegations that the government has sought to suppress investigations into the scandal have been reinforced by a rift in the public prosecutor's office.
On Monday, senior prosecutor Yun Seok-Yeol, who had led the probe into the NIS until his dismissal last week, told a parliamentary committee hearing that he had come under pressure to soft-pedal the investigation.
Yun was dismissed from the case on Thursday after he arrested three NIS agents suspected of writing posts as part of the smear campaign.
He was accused of not following protocol, but Yun suggested the real reason was the progress his probe was making.
While the number of anti-Moon and pro-Park posts emanating from the NIS had initially been put at less than 100, Yun said his team had found that agents had posted nearly 60,000 incriminating Twitter messages.