The main opposition Liberty Korea Party on Monday ramped up its claim of a government attempt to control the media, drawing fire from the ruling party that urged a united front amid North Korea's escalating nuclear threats.

Dozens of LKP lawmakers visited the prosecution and Korea Communications Commission to protest a court's recent issuance of a writ to detain MBC CEO Kim Jang-kyom over alleged unfair labor practices, arguing it is a scheme to hold sway over public broadcasters.

The conservative party has declared a boycott of all parliamentary sessions, except security-related ones, heralding an intense political standoff during its 100-day regular session that began last Friday.

During a meeting with Prosecutor-General Moon Moo-il, LKP floor leader Chung Woo-taik demanded he explain his stance over Kim's warrant, which he claimed has never been witnessed, even under the former military-backed governments.

Moon, in response, stressed that the prosecution has never received any outside directive that compromises its political neutrality and independence.

"We are deeply thinking to make the right judgment over the clash between the legal requirements (for the warrant) and the constitutional value of press freedom," Moon told the group of LKP lawmakers.

During a visit to the KCC, the LKP lawmakers repeated that the warrant issuance is an act that undermines the independence and fairness of the press.

The ruling Democratic Party called for their return to parliament, criticizing their absence at the time of a security crisis triggered by Pyongyang's sixth and most powerful nuclear test to date on Sunday.

"We doubt that their claim of being a security-focused party is just empty talk," Kang Hoon-sik, the party's spokesman, told reporters. (Yonhap)