More than 30 Wales football fans have been arrested in Armenia ahead of the European Championships qualifying game.
About 1,200 supporters are in the capital Yerevan for Saturday's match.
The Football Association of Wales (FAW) confirmed that 32 fans had been arrested, while the Foreign Office is involved.
South Wales Police officers in Yerevan said no action had been taken against the arrested fans and they were trying to find out what happened.
Supporter Lefi Gruffudd described his anger, saying it was a total shock after he was arrested with a group of friends following an enjoyable night in the city.
Another fan suggested about 25 of them were put against a wall and teased about getting six-month sentences.
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"The three of us were walking back towards the hotel last night quite late and police cars came straight up to us, took us into their cars, arrested us, kept us in custody until 3.30 this afternoon [Saturday]," Mr Gruffudd said.
"They treated us insultingly, no water, no cell, nothing through the night.
"No explanation why we were arrested and we have been asking questions all the time but no answers. We haven't slept at all and we're angry."
He said: "It's a shock, we didn't expect this, we loved the place.
"We were very happy with the people in the bars last night, there was a very good atmosphere but this was a big shock for us all."
He added: "I found out that they claim that there was a fight between the Welsh fans but we know nothing about that obviously, and I doubt if that happened but that's the reason they give us."
Many are believed to have been arrested on Friday, with some released by 15:00 local time (11:00 GMT) on Saturday, ahead of the 18:00 kick-off time.
"I have to be honest with you. I'm still a bit miffed as to what happened," said another fan, Gerallt Dafydd.
He had been for a few drinks in a bar with a group of friends.
As they waited for a taxi, he described police coming "from absolutely nowhere", adding: "They were very aggressive and handcuffed us all.
"They chucked us into the back of a police car essentially and then even in the police car were quite violent in terms of striking myself in the face, in the back seats when I when I was talking, so it was a bit of a traumatic experience."
He described about 25 fans being put against a wall with police "taking photos and laughing and that was a common theme throughout".
Mr Dafydd described fans getting emotional as he believed officers were teasing them saying they would get sentences of six weeks or six months.
He was adamant that fans did nothing wrong, adding: "They basically gave us a statement in there to say 'OK, you've done nothing wrong. Sign here'."
In a statement, the FAW said: "We are aware of the situation and we are in regular discussions with the travelling police and FSA Cymru (Football Supporters' Association) monitoring the situation.
"FSA Cymru are the fan embassy who have contact with the local authorities as well as South Wales Police who are here to liaise with local law enforcement."
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Supt Steve Rees of South Wales Police, who is in Armenia, said: "We are aware of an incident during the early hours of Saturday in Yerevan which resulted in 32 Welsh fans being arrested.
"We are working with the fan embassy and local law enforcement to find out exactly what has happened.
"Welsh fans have a good reputation when travelling abroad so this is very much out of the ordinary.
"A delegation of Welsh police officers will continue to be visible to the travelling fans during this away fixture, providing advice and helping to keep them safe."
The Foreign Office said: "We are supporting the families of a number of Welsh football fans in Armenia and are in contact with the local authorities."
The incident follows a warning from a female fan on Friday about a distressing taxi journey where the driver allegedly got in the back with her and asked for "sexual favours" instead of payment.
A victory against Armenia could see Wales qualify for Euro 2024 in Germany, if Croatia lose to Latvia.
However, victory on Saturday, and against Turkey on Tuesday, would seal the team's passage to the tournament regardless of other results.