A homeless man suffered burns after the tent he used for shelter was set on fire in a city centre.
The unnamed rough sleeper was taken to hospital after the incident in Cardiff on Monday.
Police are investigating the incident, in Queen Street in the Welsh city, as criminal damage.
A spokeswoman for the South Wales constabulary said: "At around 1.30pm on Monday, officers on patrol in Cardiff city centre received information about criminal damage to a tent in Queen Street.
"One man suffered a minor hand injury, which required hospital treatment, and inquiries are being made to identify the person responsible."
A spokesman for the Welsh Ambulance Service confirmed its staff attended and took the man to the University Hospital of Wales.
Matt Downie, director of policy and external affairs at homelessness charity Crisis, said: "For anyone sleeping on the street, life can be a struggle just to survive. Rough sleepers are 17 times more likely to be victims of violence and 15 times more likely to suffer abuse.
"Perhaps equally troubling, our research shows 53 per cent of abuse and violence against rough sleepers goes unreported to the police, mainly due to the expectation that nothing will be done.
"With at least 9,000 people across Britain sleeping rough this winter, and thousands more hidden in cars, tents and on public transport, significant action can't come soon enough.
"In the short term, it's vital that the victims of these disproportionately frequent attacks feel able to approach the authorities for support. But ultimately, they must also be given the dedicated help they need to leave the streets behind for good."
Cardiff Council said members of its homelessness outreach team had accompanied the man to hospital for treatment.
The authority said it would continue to encourage homeless people to use shelter and hostel accommodation available in the city.
A spokeswoman for the council said: "We're appealing to all those who sleep out at night to come into the wide range of accommodation in the city and begin using the services that can help move them away from life on the streets."
