Three policemen were hurt when Newcastle United fans clashed with officers in the city centre after their team were beaten 3-0 at home by Sunderland in a Premier League derby at St James' Park on Sunday.
Northumbria Police said in a statement that 29 arrests were made, less than 24 hours after Millwall fans disgraced their club by fighting among themselves during their FA Cup semi-final defeat by Wigan Athletic at Wembley.
Fourteen people were arrested on Saturday, 12 Millwall supporters and two from Wigan, on charges including affray, public order offences, assault on police and possession of drugs. Four police officers sustained minor injuries.
Sunday's trouble started in Newcastle city centre and Northumbria police tweeted information as the situation unfolded.
Newcastle fans threw bottles and set rubbish bins on fire as mounted police tried to move the home fans back to allow the visiting supporters into a railway station for their short journey back to Sunderland, 13 miles (20 kilometres) away.
"There have been pockets of disorder involving NUFC in Newcastle city centre. No major disruption, officers are on the scene and dealing with it," the police said.
"CCTV and evidence is being gathered and action will be taken against anyone involved in these sporadic incidents in Newcastle."
Local reports indicated that a flare was thrown by Newcastle fans at Sunderland supporters before kickoff and the Sunderland team bus was greeted by hostile hordes of Newcastle fans as it arrived at the ground.
Photographs on websites showed angry Newcastle fans in clashes with police.
The game ended in a resounding victory for relegation-threatened Sunderland, their first win at their rivals since 2000 and their biggest victory in Newcastle since 1966.
Police said on their website (www.northumbriapolice.uk) before the match that extra patrols would be in force in Sunderland and Newcastle to prevent trouble.