North Korea has issued thinly-veiled criticism against South Korea's prosecutors over their recent raid on the minor opposition Unified Progressive Party (UPP), some of whose members are accused of pro-North Korea stances.

Prosecutors seized three computer servers of the UPP on Tuesday after an 18-hour standoff between investigators and party officials. The surprise raid comes amid internal strife over how to revive the party torn apart by allegations of a rigged primary.

The servers contain information on the party members, though computer programs used in the primary designed to select its proportional representation candidates for the April 11 elections remained missing.

The North's official Korean Central News Agency reported the party's condemnation against prosecutors over the raid in what could be Pyongyang's indirect criticism against South Korea.

The raid was an "explicit politically-motivated suppression and a revelation of the sinister intention to shake the foundation of the progressive party," a party official said in a news conference in Seoul on Tuesday, according to a KCNA dispatch on late Thursday.

The five-month-old party is in a crisis over separate accusations that some of its lawmakers-elect and rank-and-file party members embraced North Korea's guiding "juche" philosophy of self-reliance.

The North's apparent criticism came amid a looming standoff between the party's two rival factions over how to handle the fate of two lawmakers-elect and 12 other candidates accused of being involved in the rigged primary.

Six of the 14 candidates were elected as UPP lawmakers last month under the proportional representation system, which allocates seats to parties according to the numbers of votes they receive.

The party has given the 14 people a second ultimatum to resign by Friday noon or face expulsion. The left-wing party said 10 out of 14 have either tendered their resignations or expressed intention to do so, though two lawmakers-elect and two other candidates rejected the ultimatum.

Lee Seok-gi and Kim Jae-yeon, the two lawmakers-elect, would become independent lawmakers-elect if they are expelled from their party. The two were both convicted of engaging in pro-North Korean activities in the past.

Meanwhile, Lee Sang-kyu, a UPP lawmaker-elect who won a directly contested seat in a southern Seoul district, said in an interview on the local MBC radio station that the North's three-generation hereditary power succession should not be considered a sin, though it is problematic.

Lee also said he is opposed to North Korea's nuclear weapons programs.

His remarks came amid public criticism over his recent refusal to answer questions during a live television program about North Korea's human rights record, nuclear programs and the power succession.

North Korean leader Kim Jong-un took over the country following the December death of his father, long-time leader Kim Jong-il. The late Kim himself inherited power upon the 1994 death of his father, the country's founder Kim Il-sung. (Yonhap)