Opposition parties on Wednesday castigated North Korea's threat of military strikes against South Korea and the United States, urging Seoul to toughen its stance against the belligerent regime.

Earlier in the day, Pyongyang threatened to launch missile strikes to lay siege to US strategic military installations in Guam. On Tuesday, the communist state took issue with Seoul's maritime live-fire drills, warning Seoul could be turned into a "sea of flames."

"We strongly condemn the series of the North's provocations, including its threat of strikes near Guam," Khang Hyo-shang, the spokesman of the main opposition Liberty Korea Party, said in his commentary.

"The North's attempts at extending its regime's life by launching armed provocations and threatening peace in East Asia are unacceptable," he added.

The North's continued saber-rattling has provided political fodder for the conservative bloc to accentuate its professed security forte and sharpen criticism of the liberal ruling camp's traditionally dovish stance. 

Chung Woo-taik, the LKP floor leader, renewed his call for President Moon Jae-in to change his North Korea policy entailing both dialogue and sanctions, portraying it as unrealistic and ineffective.

Chung, in addition, repeated his party's stance that the government has to adopt a more aggressive defense posture by securing nuclear-powered submarines and pushing for the redeployment of US tactical nuclear arms.

The People's Party also joined the chorus of criticism over Moon's policy toward the North.

"Despite the North's day-to-day threats and US' tough stance, our government does not make any (strong) responses," Son Kum-ju said in his commentary. "Is this what he describes as taking the driver's seat in addressing peninsular issues?"

Joo Ho-young, the floor leader of the Bareun Party, underscored growing public concerns over the North's menacing rhetoric, urging the Moon government to show a stable and consistent hand over its security policy.

"When the North keeps advancing its nuclear program, there seems to be no clear strategy and policy direction," Joo said during a party meeting. (Yonhap)