National police chief Yoon Hee-keun apologized Tuesday over the weekend Halloween crowd crush, saying he feels "heavy responsibility" and vowing to look thoroughly into what went wrong with the police response.

Yoon, commissioner general of the National Police Agency, made the remark amid criticism of the police response to the Halloween crowd surge that has left at least 156 people, mostly in their 20s, killed and 30 others seriously injured in South Korea's deadliest disaster in eight years.

"I wish for a quick recovery of those who were injured and feel heavy responsibility for the people who got a huge shock," Yoon told a press conference. "In order to clearly uncover truth and determine responsibility, we will conduct an intensive inspection and investigation into all areas in a swift and thorough manner."

Yoon said an independent body will be set up within the National Police Agency.

He also acknowledged shortfalls in the police response.

"It was confirmed that there were multiple 112 emergency reports alerting the severity of the situation at the scene right before the incident," Yoon said.

Later in the day, Yoon said a total of 11 calls were received from hours before the incident erupted.

"I have confirmed that 11 emergency calls warning of the potential danger and urgency at the scene were made starting around 6:34 p.m. on the day of the incident," Yoon told a parliamentary session. "It is judged that the response in the field handling emergency calls was insufficient."

Separately, the NPA launched an inspection into the Yongsan Police Station in charge of policing Itaewon to determine if the station provided proper safety management services for Halloween gatherings on the day. (Yonhap)