Conservative parties on Monday raised speculation that South Korea was bypassed by the United States in the latter's decision to fly a fleet of bombers and fighters near North Korea's east coast in the latest show of force against the wayward regime.

Although the presidential office Cheong Wa Dae said the rare flight on Saturday night followed the allies' prior coordination, the parties demanded President Moon Jae-in explain the situation and craft measures to prevent what they term "Korea passing."

Escorted by F-15 fighters from Kadena Air Base in Okinawa, US B-1B Lancer bombers from Andersen Air Force Base in Guam carried out the mission, which Washington said underscored "the seriousness with which we take (the North's) reckless behavior."
 

The flight came after US President Donald Trump and North Korean leader Kim Jong-un traded barbs. During a UN speech last week, Trump called Kim a "Rocket Man on a suicide mission," threatening to "totally destroy" the North. Kim, in turn, cast Trump as "mentally deranged."

"The US independently carried out an unprecedented military operation to fly its bombers and fighters north of the Northern Limit Line for the first time since the Korean War (1950-53)," Chung Woo-taik, the floor leader of the main opposition Liberty Korea Party, said during a party meeting. The NLL is the de facto inter-Korean sea border.

"Cheong Wa Dae and the government have to explain to the National Assembly and citizens why such a military operation just short of a war came with South Korea being excluded from it, and what kind of cooperation there was on that matter between Seoul and Washington," he added.

Critics here noted that the flight of US warplanes might signal that Washington could stage unilateral military operations without consulting Seoul first in the case of a major North Korean provocation.

Such worries have persisted as observers pointed to a possible policy gap between the allies. Seoul has stuck to its policy of engagement with Pyongyang, while Washington has mentioned a possible military option and employed a raft of sanctions, both unilateral and multilateral.

Chung also renewed calls for a "wholesale" change of Moon's policy towards the North, criticizing his pursuit of dialogue with it and his plan to provide humanitarian aid to it via international agencies.

The minor opposition Bareun Party also voiced concerns that Seoul could be sidelined in important security issues involving the Korean Peninsula.

"There are many who say just the fact that the B-1B bomber crossed the NLL without the help of the South Korean Air Force shows the US' will to strike the North on its own, and that the South was sidelined in that process," Joo Ho-young, the party's floor leader, said during a meeting with senior party officials.

"This government must put forward its blueprint of how to address the nuclear standoff ... It doesn't seem to have any measure other than dialogue when the North's nuclear program was advancing," he added.

The ruling Democratic Party, meanwhile, called for "bipartisan cooperation" in handling security issues. (Yonhap)