Police have raided the office of an anti-election fraud group linked to former Prime Minister Hwang Kyo-ahn on suspicion of illegal electioneering.

The Seoul Metropolitan Police Agency said it searched the group’s Yongsan office for five hours on Wednesday, seizing computers and documents.

Hwang and the group are accused of mobilizing a nationwide network of some 500-thousand members to back his independent presidential bid in the 21st election in June, in violation of election law.

The Election Act bars organizations established or run by parties or candidates from engaging in activities that could influence voters within 180 days of an election.

Authorities say the group held rallies, promoted Hwang in online chat rooms, posted links to his campaign sites, and circulated reports suggesting election fraud to sway public opinion.

The raid followed a complaint filed in May by the National Election Commission alleging unlawful campaigning and interference in voting.

Hwang denounced the investigation as “political persecution,” while his lawyer argued police mistakenly raided his party office rather than the group’s headquarters.