Prosecutors are looking into allegations that former and current executives of the nation's major mobile carrier KT offered money to lawmakers.

The Seoul Central District Court recently called in a spokesperson of the firm's labor union and the head of a civic group, who filed a complaint against the firm.

The accusers reportedly testified that KT executives had offered illegal donations to politicians using funds from the company and personally pocketed part of the money when the donations were returned later.

In a separate probe, the prosecution is looking into allegations that KT's incumbent top executives, led by Chairman Hwang Chang-gyu, created a one-point-one billion-won slush fund between May 2014 and October 2017, and spent about 438 million won of the money to bribe some 99 lawmakers.

Police had initially investigated the case as embezzlement, but the prosecution is looking into the case from scratch, after a separate probe into an alleged unfair hiring by KT of a lawmaker's daughter.