Three police officers suffered minor injuries after being pelted with missiles including bottles while responding to “violent disorder” near the Welsh Parliament.

A 21-year-old man and a 16-year-old boy were arrested on suspicion of public order offences and a knife was recovered after crowds of mostly young people gathered outside the Senedd on what was the hottest day of the year on Tuesday.

The area outside the Senedd in Cardiff Bay was left littered with rubbish including bottles, cans, packaging and plastic bags where more than 100 people had congregated.

On Wednesday South Wales Police said an “incident of violent disorder” broke out around 10pm on Tuesday, after which the two individuals were arrested and released on bail.

It said an investigation was under way to identify further participants of the disorder.

A spokesperson for the force said: “During the course of the disturbance a number of missiles, including bottles, were thrown at officers. Three suffered minor injuries.”

Police had positioned themselves outside the Senedd to observe the crowd, with the building’s steps recently becoming a hotspot for gatherings since the nearby Oval Basin was fenced off by Cardiff Council to discourage people from meeting in large numbers.

Welsh Government Covid-19 rules mean people can only meet in groups of up to six people from two different households, while two-metre social distancing must be maintained from people not part of your household or extended household.

Chief Inspector Tony Williams said most people who entered the bay area on Tuesday evening followed restrictions and police were present to remind people of health regulations.

“Crowds were dispersed at various points through the evening, and at around 10pm, officers were required to intervene in an incident of violent disorder in Cardiff Bay,” he said.

“Two people were arrested and a knife was also recovered from one of the suspects.

“The violence levelled at officers was despicable and will not be tolerated, nor will we tolerate the anti-social behaviour and criminality displayed by the minority on Tuesday evening.”

He said police would continue to work with the council and Welsh Government to consider further measures over the bank holiday weekend, when there will be increased patrols in popular areas.

Wales’s health minister Vaughan Gething commented on the disorder on Twitter, saying: “Completely unacceptable behaviour.

“(Police) officers should not be subjected to this and the public will be deeply unimpressed. We’ve all made sacrifices to keep Wales safe – we still have responsibilities.”

First Minister Mark Drakeford tweeted: “Behaviour such as this is unacceptable.

“We all have a personal responsibility to keep others safe, to respect each other and our beautiful shared public spaces.”