A large fire has broken out in one of Berlin's biggest city forests, triggered by several explosions that took place at an ammunition dump inside the forest.
About 100 firefighters were battling the blaze in the German capital's Grunewald forest in the west of the city, German news agency DPA reported.
The fire was spreading quickly and massive explosions could be heard from the site where old ammunition from the Second World War, fireworks and explosive ordnance are stored and controlled explosions are carried out.
"The situation is dangerous," Thomas Kirstein from the Berlin fire department told reporters.
"The fire is not under control, the forest is burning uncontrollably."
He said it was not clear what triggered the first explosions at the ammunition dump early on Thursday.
He called on residents to stay away from the forest.
Due to flying debris and the threat of further explosions, the fire department said it had not yet begun to systematically extinguish the blaze as emergency forces had to keep more than half a mile from the flames.
Firefighters on the scene were pouring water on the forest outside the banned area around the ammunition dump trying to prevent the blaze from spreading further.
In a tweet, the Berlin fire department reported there had been many explosions in the Grunewald forest, adding that authorities had sealed off an area with a 1,000-meter radius.
The fire service said that the blaze had spread across 15,000 square metres and delivered a firm warning to not enter the forest area.
"The plan is to get a new situation assessment from the blast site - initially from the air," Mr Kirstein said, adding that they hoped to access the area with armoured vehicles later in the day.
According to first estimates, an area of 1.5 hectares was burning on Thursday morning.
Berlin authorities called for additional task forces to help extinguish the flames, including special forces from the army.
Water cannons and special evacuation tanks were also due on the scene.
The commuter train service to the city's west was partially interrupted and one of the city’s most important highways, the Avus, was closed.
Homes were not directly threatened by the flames but the fire department warned that the blaze could spread due to the dry conditions of the forest and expected temperatures of up to 38C.
Berlin is currently facing a weather warning. German weather service DWD forecast one of the hottest days of the year yet with temperatures on Thursday expected to range between 34 and 38 degrees Celsius.