Police have launched an investigation into claims that high-ranking police officers tried to affect the outcome of a police probe into allegations that government spy agents intervened in December's presidential election, an official said Tuesday.

The probe comes after Kwon Eun-hee, a police officer who led the investigation into a spy agency scandal at Seoul's Suseo Police Station, disclosed Friday that high-ranking national police officers had tampered with the police probe.

The National Police Agency (NPA) on Monday questioned police investigators, including a chief investigator of the Suseo Police Station, to look into Kwon's claims, the official said.

"It is a process to look into all suspicions whether there was a problem during the investigation or Kwon's claims were inflated," the officer added.

Wrapping up a four-month-long probe, the Suseo Police Station announced Thursday that two National Intelligence Service (NIS) agents had illegally intervened in politics by posting a slew of politically sensitive comments on the Internet ahead of the Dec. 19 presidential vote.

A day later, Kwon argued that officials of the Seoul Metropolitan Police Agency (SMPA), which oversees all police stations within Seoul, had unfairly intervened with the probe. The comment sent ripples through political circles and the nation's intelligence agency.

As an example of undue influence from her superiors, Kwon cited that her team initially had asked SMPA to analyze all computer files that included 78 key words but the agency later cut that number down to four.

SMPA officials, however, refuted Kwon's claim, arguing that they had never unilaterally asked her to reduce the number.

She also further disclosed that she had received a phone call from one of her superiors not to disclose to the press any details regarding the probe.

Amid mounting suspicions and criticism from the opposition party, NPA Commissioner Lee Sung-han pledged Monday to investigate the claims.

Separately, the Seoul Central District Prosecutors' Office also launched a special investigation team to look into the scandal upon receiving initial probe results from the police. (Yonhap News)