Police have formed a special team to investigate an illegal gathering that disrupted the New Year's eve celebration at Dataran Merdeka.

Kuala Lumpur police chief Datuk Mohmad Salleh said with the setting up of the team, police hoped to complete investigation of the case within a week.

"We put this investigation as a priority because this is the most important case. Give us a week," he told reporters at the Kuala Lumpur police contingent headquarters on Wednesday.

On quarters responsible for staging the illegal gathering, Mohmad said he did not rule out the possibility of four non-governmental organisations (NGOs), which had been named by the police earlier.

Police had named four NGOs as organisers of the event, namely Gerakan Turun Kos Sara Hidup (TURUN), Solidariti Mahasiswa Malaysia (SMM), Jingga 13 and Solidariti Anak Muda Malaysia (SAMM).

"We will investigate because they have disrupted public order during the New Year eve celebration.

"Based on police observation, there were about 25,000 at Dataran Merdeka, including those who came to celebrate the New Year," he added.

However, the New year's eve concert at the Dataran Merdeka had to be called off about 30 minutes before the countdown when protesters broke through the police cordon to seize the stage Mohmad said police had received 1,936 reports from NGOs and individuals against the gathering.

Eight police reports had also been lodged over the gathering, which, he said, included on the discovery of four machetes and three Rambo knives which were found hidden in an umbrella behind the Dayabumi Complex.

Mohmad said a report was also lodged on a police officer who was injured on the head and lips when hurled with canned drinks by protesters while on duty at Bukit Bintang.

However, no arrest has been made so far, he added.