A holidaymaker dressed as a clown prompted a mass brawl on a cruise ship in which passengers used furniture and plates as weapons, according to witnesses.

The late-night fight in the buffet area onboard P&O’s Britannia left a member of staff injured as they tried to intervene while onlookers fled in fear.

The brawl, which took place in the early hours of Friday morning during the return leg of a week-long cruise to Norway’s fjords, reportedly followed an alcohol-fuelled afternoon of “patriotic” partying on deck.

The perpetrators were said to have been confined to their cabins for the last day of the cruise. A 41-year-old woman and a 43-year-old man from Essex were arrested by Hampshire police on suspicion of assault when the ship docked in Southampton on Saturday morning.

Six people, including three women, were assaulted during the fight, resulting in a series of injuries including “significant bruising and cuts”, the force said. One of those injured was a staff member.

Richard Gaisford of ITV’s Good Morning Britain, who was on the cruise, said he was alerted to the incident when a 2am emergency tannoy announcement called for security to rush to the 16th floor restaurant.

Gaisford tweeted on Saturday: “‘There was blood everywhere’. Violent late night brawl in the buffet onboard P&O Cruises’ Britannia left staff who intervened injured, as passengers used furniture and plates as weapons. Witnesses told me they were so frightened they had to hide, as family groups fought.”

He said that, after hearing the tannoy, he went to the restaurant where he found “shocked” passengers. “One witness, part of a group involved in the trouble, explained to staff that things kicked off when another passenger appeared dressed as a clown. This upset one of their party because they’d specifically booked a cruise with no fancy dress. It led to a violent confrontation,” he wrote.

He added: “Britannia left Bergen at 14.30 on Thursday, the violence occurred 12 hours later after a black-tie evening. It followed an afternoon of ‘patriotic’ partying on deck, with large amounts of alcohol being consumed by many guests.

“The buffet area was immediately sealed off as medical teams went to help the injured. Staff told me they’d never experienced anything like it and those behind the violence were confined to a cabin for the last day of the cruise, waiting for police here in Southampton.”

Hampshire police said: “Officers are investigating following reports of a public order incident onboard P&O’s Britannia. The incident happened during the early hours of Friday 26 July while the ship was en route to Southampton from Bergen.

“Six people – three men and three women – were assaulted. A number of injuries were suffered including significant bruising and cuts.

“Investigations are ongoing. Two people, a 43-year-old man and a 41-year-old woman, both from Chigwell, Essex, have been arrested on suspicion of assault and are currently in police custody.”

A P&O Cruises spokesman said: “Following an incident onboard Britannia on Thursday evening we can confirm that all guests have now disembarked and the matter is now in the hands of the local police.”