What's the truth?: While the video is indeed from Greece, it dates back to 2019.
It shows a clash between migrants and the police at Diavata in Northern Greece after the migrants were stopped from crossing the border.
How did we find out the truth?: On performing a reverse image search on some of the keyframes of the video, we came across a Facebook post from 30 June 2019.
The post carried the same viral video and mentioned the location as Diavata, Greece and date as '04-05-19'.
It also mentioned that the video shows refugees.
Taking a cue, we performed a relevant keyword search and found several old reports about a clash between migrants and police.
A report in the Daily Mail said that some migrants set up fires to disperse the fumes left by the tear gas shells.
The police clashed with the migrants when they stopped several people from illegally crossing through the Balkans to northern Europe.
It also stated that this was a follow-up reaction to the viral rumours about the restrictions being lifted, which kept the migrants from travelling to Northern Europe.
We also found a picture on Getty Images of a woman with her two children, one in a pink jacket and another in a black stroller, which matched the one seen in the viral video.
What about the current forest fires in Greece?: Greece witnessed deadly wildfires for two weeks starting on 17 July.
These were finally abated on 28 July.
This also resulted in rising temperatures and strong winds which killed five people, destroyed farms and homes.
Conclusion: An old video from Greece showing a clash between the police and the migrants is being falsely shared as 'illegal migrants' starting the forest fires.