SEOUL, South Korea -- South Korean police on Friday blamed negligence and planning failures for last year's Halloween crowd crush in Seoul that killed more than 150 people.

Scores of young costumed partygoers, mostly women in their 20s, died in the disaster on October 29 in the capital's popular Itaewon nightlife area.

A special team that spent months combing through evidence and interviewing officials, said at the end of its probe that there had been massive planning and response failures -- but stopped short of blaming any top government or national policy agency officials.

"Organisations that are legally obligated to prevent and respond to disasters -- police, district offices and Seoul Metro -- did not establish safety measures in advance or came up with poor plans," Sohn Jae-han, the team's head, told reporters.

"Appropriate measures were not taken even after receiving rescue requests" on the day of the disaster, he said.

Poor cooperation between agencies and delays in communications and relief efforts contributed to a higher death toll, he added.

Six people have been arrested due to the probe -- including Lee Im-jae, the former head of the Yongsan Police Station, which oversees Itaewon, and Park Hee-young, the head of the Yongsan district office.

Both Lee and Park are being held in detention on charges of professional negligence resulting in death.

In December, a teenager who had survived the crush was found dead in an apparent suicide, with officials ruling he should be considered a victim of the disaster, and raising the death toll to 159.

No top government officials liable

But the team did not blame any officials from the Seoul city government, the interior ministry, or the national policy agency, Sohn said, as it was "difficult to conclude that there was a concrete violation of duty".

Interior Minister Lee Sang-min has faced mounting pressure to step down over the tragedy.

Shortly after the crush, he was widely criticised for claiming that having more fire department and police personnel in Itaewon would not have prevented the disaster.

He has since repeatedly apologised -- including in person last week to the families of the victims -- but has not offered to resign.

South Korea's rapid transformation from a war-torn, impoverished backwater to Asia's fourth-largest economy and a global cultural powerhouse is a source of its national pride.

But a series of preventable disasters -- such as the Halloween crush and the 2014 Sewol ferry sinking that killed 304 people -- has shaken public confidence in the authorities.