The rival parties on Monday traded accusations over the violence at a rally in central Seoul on Saturday that left dozens of protesters and police officers injured with one in critical condition.

The ruling Saenuri Party defined it as an “illegal political rally” that was attended by a police-estimated 64,000 people against the government’s state-authored history textbooks, labor sector reform and free trade agreements. The main opposition New Politics Alliance for Democracy accused the authorities of using “excessive violence against the people” and illegal counteraction.

Both vowed to take stern measures against those responsible as the political standoff aggravated over a number of contentious issues including security, education and economy as the parties head toward the parliamentary race next April.

“These so-called professional demonstrators who aim to push society into confusion made the Gwanghwamun area, the heart of this country, into a lawless world,” Saenuri chairman Rep. Kim Moo-sung said. 

Saenuri floor leader Rep. Won Yoo-chul questioned their motive citing the distribution at the site of papers that were written with phrases like “Oppose dissolution of the UPP” or “Release Lee Seok-ki.” The Unified Progressive Party was dissolved by the Constitutional Court last year citing its plot for a rebellion. UPP lawmaker Rep. Lee Seok-ki was convicted of plotting to overthrow the government in the event of a war with the communist North.

“We must firmly trace whether there were any rebellious forces behind the rally,” Won said.

Their remarks were echoed by other senior and rookie members of the party with some likening it to a “riot,” and some comparing it to last week’s Paris terrorist attacks by saying, “Violence that is controlled by radical antiestablishment forces must be removed fundamentally.”

The NPAD, meanwhile, called the incumbent government “abnormal” for dealing with “innocent people with violence.”

“This government only excels in killing the people’s livelihood and oppressing the public,” said NPAD chairman Moon Jae-in. “It must listen to the outcry of the people against youth unemployment, the retrogressive revision of the labor law and price slump of agricultural products.”

NPAD Rep. Joo Seung-yong citied the 2011 ruling by the Constitutional Court that found police buses barricading the Seoul Plaza as unconstitutional for blocking citizens’ right for free movement, calling the latest barricade unconstitutional.

The party’s floor leader Rep. Lee Jong-kul said the serious injury suffered by demonstrator Baek Nam-gi, who underwent brain surgery after he fell as police doused him with water cannons, was equivalent to the Sewol ferry captain “murdering” the passengers -- referring to Lee Jun-seok, who was sentenced to life imprisonment for neglecting his duty to evacuate passengers when the ferry sank off in April 2014, killing 304.

The protests, arranged by the Korean Confederation of Trade Unions and joined by labor, civic and farmers’ groups, turned violent on Saturday afternoon as police clashed with demonstrators attempting to march through Gwanghwamun Square toward the presidential office by pulling down barricades set up by police buses.

The clashes left one critically injured, 51 arrested and 50 police buses damaged. Some 113 police officers were wounded while the KCTU claimed at least 500 were injured by the “excessive police force.” A total of 182,000 liters of water and 651 liters of capsaicin were used.

From news reports