More than 15 people have been killed and 24 injured in a shooting at a university in Prague, officials say.
Police said the gunman had also been "eliminated" following the shooting at Charles University - the deadliest attack in modern Czech history.
Prime Minister Petr Fiala said he had cancelled upcoming engagements in light of the "tragic events" on Thursday.
University staff were told to stay put, barricade themselves in rooms and turn off the lights.
Footage has emerged on social video showing terrified crowds fleeing the area popular with tourists.
Police received first reports of shooting at the university's Faculty of Arts on Jan Palach Square in the centre of the capital after 15:00 local time (14:00 GMT).
At a briefing later on Thursday, the police and city authorities said the gunman was a student at the faculty.
They said he was a 24-year-old from a village 21km (13 miles) outside Prague. The suspect's father had been found dead earlier on Thursday.
The gunman's motives were not immediately known.
Preliminary information suggested that no police officers were injured in the attack, the authorities said.
Sergey Medvedev, a professor at the university, told the BBC he was in the auditorium when the shootings began.
"I was giving a lecture at the moment and at first didn't quite realise what happened because there were some sounds. The students, I think, heard it better because I was so much concentrated on my talking, on my lecture," he said.
"Then... we understood that something big is happening. There was nothing online yet, nothing in the Czech press and the [news] networks. Then at some point, the special operation groups went storming in, they searched the room briefly and then went out... they told us to stay inside.
"One hour later, another police squad broke in and then put us on the floor, briefly searched us then evacuated from the building," the professor added.
Verified images from the scene appeared to show people clinging on to the outside wall of the university building, several storeys up.
Targ Patience, a British-Australian who was staying in a flat near the scene, told the BBC that he heard "a lot of gunshots".
"I looked out of my balcony and saw the police arrive. A few officers were having a hard time stopping people walking towards the scene," he sad.
"We heard four loud gunshots," Joe Hyland, 18, from Truro, Cornwall, told the BBC. "Everyone was sprinting and running for cover.
"I have a bad knee, am on a crutch. So I hobbled as quickly as possible," added Mr Hyland, who was on his first holiday with friends. "We got to the metro and went down there because we thought it would be safest."
Students said they had barricaded themselves in classrooms.
"Currently stuck inside my classroom in Prague," Jakob Weizman, a student at Charles University, wrote on X (formerly Twitter) as it unfolded.
"Locked the door before the shooter tried to open it."
European Commission President Ursula von der Leyen wrote on X that she was "shocked by the senseless violence". She added: "We stand and mourn with you."
An email to staff at the philosophy faculty of Charles University, seen by Reuters, warned staff of the shooting.
It read: "Stay put, don't go anywhere, if you're in the offices, lock them and place furniture in front of the door, turn off the lights."
Authorities said the whole of the square and several streets around the university were closed.
Charles University is located in Prague's Old Town, about 500m from the historic Charles Bridge, a tourist magnet.