Greek authorities arrested 13 people on Saturday after fireworks launched from a yacht set off a forest fire on an island near Athens as the country confronts a new season of deadly summer fires. The mayor of the island of Hydra expressed “outrage” after the fire was started late on Friday and vowed legal action against those responsible. Dozens of wildfires in Greece this week have left at least one person dead. The latest blaze was “caused by fireworks launched from a boat and burned the only pine forest on the island in a place that is difficult to access and has no road”, Hydra’s firefighting team said on Facebook. Thirteen people accused of involvement in the fireworks have been arrested after a fire service inquiry and will be presented before a prosecutor on Sunday, said a fire service statement. No details on the suspects were given. Greece has toughened its penalties for arson, with perpetrators now facing up to 20 years in prison and fines of up to 200,000 euros (£169,000). On top of calling for legal action against the “irresponsible” people behind the fireworks, Hydra’s mayor Giorgos Koukoudakis told the ERT public broadcaster that authorities had to create more anti-fire zones and roads through forests. Another fire raged on Saturday on the island of Andros, emergency services said. Four villages were evacuated and planes and helicopters were brought in to water-bomb the flames. The civil protection service called for extreme vigilance because the risk of fires was “very high”, particularly in the Attica region, the Peloponnese peninsula and in central Greece. Greece has been bracing for a difficult summer as authorities warn that strong winds and high temperatures have increased the danger. After its warmest winter ever, the Mediterranean country recorded its first heatwave of the year last week, with temperatures rising above 44C (111F) in some locations. Firefighters on Friday battled wildfires fanned by three days of fierce winds that left at least one person dead, a 55-year-old man who collapsed and died while fighting flames around his village. Last year, a fierce two-week heatwave was followed by devastating wildfires in which 20 people died. Scientists warn that fossil fuel emissions caused by humans are worsening the length and intensity of heatwaves around the world. Rising temperatures are leading to extended wildfire seasons and increasing the area burned by the blazes, according to the UN Intergovernmental Panel on Climate Change.