Several people have been injured after Sikh groups brandishing swords clashed at India's Golden Temple as special prayers were held to mark the deadly military offensive there in 1984.
Reports said the fight at Sikhism's holiest shrine was over who would speak first at the ceremony and that a scuffle broke out over a microphone.
Footage showed men running down temple steps lashing out with their swords.
Reports said at least three people had been taken to hospital with injuries.
The Indian government says 400 people and 87 soldiers were killed during the 1984 military raid to flush out Sikh separatists from the Golden Temple at Amritsar, codenamed Operation Blue Star.
But Sikh groups say the number of casualties was much higher and estimate it closer to 1,000.
On Friday, hundreds of Sikhs had gathered at the shrine to remember those killed in the June 6 raid 30 years ago, but the ceremony soon erupted into chaos.
Television footage showed the rival groups, sporting blue and orange turbans, fighting each other on a staircase and through the courtyard.
"Today we were supposed to have a solemn remembrance for the martyrs of 1984, so what has happened is very sad," Prem Singh Chandumajra, a spokesman for Punjab state's ruling party Shiromani Akali Dal (SAD), told reporters.
"The temple has once again been dishonoured today."
Mr Chandumajra said the clashes in the holy place were unacceptable and that the temple management would take action against those involved.
A senior police official told the BBC the situation had been brought under control and the city was peaceful.
The 1984 military operation sparked off a chain of events that led to the assassination of the then Prime Minister Indira Gandhi by her Sikh bodyguards.
That, in turn, led to days of anti-Sikh rioting in Delhi which left thousands dead - and Sikh groups argue that there has still been no accountability for either the army assault or the riots.
Earlier this year, Britain said it had given advice to the Indian military in the early stages of its planning for Operation Blue Star, and some Sikh groups are also calling for an independent investigation into this episode.