Police arrested a number of fans on Saturday after pitch invasions marred the Premier League match between Bournemouth and Newcastle and Swansea's FA Cup quarter-final at home to Manchester City.
Trouble caused by supporters entering the field of play has been in the spotlight following high-profile incidents last weekend, including an attack on Aston Villa midfielder Jack Grealish.
Seven Newcastle fans were arrested on Saturday, including a 14-year-old boy, on suspicion of invading the field of play during the 2-2 draw at Bournemouth.
A possible assault of a female steward, who suffered an injury to her nose, is also being investigated.
Travelling supporters spilled onto the playing surface at the Vitality Stadium while celebrating a stoppage-time equaliser from Newcastle winger Matt Ritchie.
"Six men and a 14-year-old boy were arrested on suspicion of going onto the playing area at a football match from the away supporters' stand and are assisting officers with their inquiries," read a statement from Dorset Police.
"One female steward sustained an injury to her nose during the incident and investigations are under way to establish whether any assault took place."
South Wales Police announced that three male youths remained in custody following two separate incidents for encroachment onto the pitch during the Swans' 3-2 defeat to City at the Liberty Stadium.
In a statement, police match commander Superintendent Steve Jones said: "The safety of supporters, players, officials and those who work these games is paramount.
"Those who invade the playing area are committing a criminal offence, will be dealt with robustly and could face lengthy bans from all football matches. We will continue to work with the football club to prevent and deter this unacceptable behaviour from a very small minority continuing."
Manchester City manager Pep Guardiola said: "It's happened a few times lately and it's a worry because in the future we could have problems.
"It's not nice but thankfully nothing happened this time."
Birmingham supporter Paul Mitchell was jailed after punching Grealish in last Sunday's second city derby, while Manchester United defender Chris Smalling was confronted by an Arsenal fan on the same day.
Those events followed Rangers captain James Tavernier being confronted by a pitch invader at Hibernian two days earlier.