Police have turned people away from beauty spots including the Brecon Beacons after hundreds of vehicles arrived at the national park.
Dyfed-Powys Police said one man had driven from Hertfordshire to walk up Pen-y-Fan, while a minibus of mixed households had travelled to the area from Cheltenham, Gloucestershire.
The force issued fixed penalty notices for some breaches.
Police forces in Wales had been forced to step up patrols and stop cars as crowds flocked to beauty spots and beaches despite lockdown travel rules.
Wales went back into an alert level four lockdown on Boxing Day after rules were relaxed for Christmas Day only.
The Welsh government restrictions only allow travel if trips are essential while “exercise should start and finish from your home” rather than involve car journeys to another location.
It comes as cases continue to surge across the UK with the NHS on the brink of being overwhelmed and the UK government facing calls to bring in tougher measures.
#COVID19 | We have received numerous reports of crowds of people at beaches and other beauty spots across #SouthWales....
Over the last few days, crowds have reportedly been travelling to beauty spots like the Brecon Beacons and Snowdonia after snow swept across the UK this week.
The car park below Pen y Fan in the Brecon Beacons was full up on Monday as people went for a walk in the area, according to the BBC.
North Wales Live also reported that crowds were seen at Pen-y-Pass and Ogwen Valley in Snowdonia as day-trippers travelled to the see snow-covered mountains.
On Tuesday, South Wales Police issued a warning after receiving numerous reports of crowds at nearby beaches and beauty spots.
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In a social media post, the force said: “We have received numerous reports of crowds of people at beaches and other beauty spots across #SouthWales.
“Please remember that Welsh Government restrictions state that exercise should start and finish at your home – you shouldn’t be driving to these places.”
South Wales Police said it has stepped up patrols and will be stopping cars to check whether the journey is essential.
It added: “Please understand that we are doing our best. However, we can’t be everywhere all of the time, it’s up to us all to do the right thing.”
Dyfed-Powys Police also warned people not to make non-essential trips.
The force posted on Twitter: “We are currently in Brecon conducting high visibility patrols.
We are currently in Brecon conducting high visibility patrols. A large number of people are visiting the area to walk up Penyfan. This is not essential travel. Officers are engaging and educating and where necessary will enforce restrictions. #StayAtHome pic.twitter.com/G2IOKK27SC
— Carmarthenshire Roads Policing 🏴 (@CarmsRPU) December 29, 2020
“A large number of people are visiting the area to walk up Penyfan. This is not essential travel. Officers are engaging and educating and where necessary will enforce restrictions.”
The force added: “There are a couple of hundred vehicles in the area.
“Officers have spoken to one man who had driven from Hertfordshire to walk up Pen y Fan, while a minibus of people from mixed households had travelled from Cheltenham.
“Fixed penalty notices have and will be issued to those blatant breaches where engagement fails, but the vast majority of people are listening to advice and when they are turning up and seeing RPU vehicles at the site, they are turning around and going home – which is the objective of our high visibility patrols.”
Aberglaslyn Mountain Rescue Organisation (AMRO) shared the Welsh government's rules on Twitter to remind the public of travel restrictions.
It also retweeted a post from the Snowdonia National Park, which told visitors: “Although the snow does look pretty on the mountains the current Welsh Government guidelines say people should only travel if it's essential. “
Aled Davies, the deputy leader of Powys County Council, told BBC Radio Wales that he was "not angry... just disappointed" to see the crowds in the Brecon Beacons.
He said: "It is very clear and very simple and it is disappointing to see so many people travelling up to Pen Y Fan.
"Just stay at home and take exercise locally, it's so important."
North Wales Police and Senedd Cymru have been contacted for comment.
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