The National Assembly on Monday passed a proposal calling for the extension of a parliamentary probe into the state spy agency's alleged meddling in last year's presidential election.

Last week, rival political parties agreed to extend the probe by eight days until Aug. 23 and summon witnesses for hearings starting this Wednesday.

The probe, which began early last month, aims to uncover the truth behind allegations that the National Intelligence Service conducted an online smear campaign to sway public opinion in favor of the ruling Saenuri Party ahead of last December's election.

The extension came as the ruling party and the main opposition Democratic Party (DP) wrangled over various terms of the probe, including who should stand as witnesses.

The opposition party took to the streets early this month to protest what it claimed was the ruling party's attempt to sabotage the investigation.

The DP has since held public rallies and taken part in candlelight vigils organized by anti-government civic groups, demanding President Park Geun-hye apologize over the scandal.

(Yonhap News)