According to the details provided, four people got seriously injured as a result of the attacks which took place in different parts of Vienna, the capital of Austria, on Wednesday evening.
Eight emergency service vehicles were present at the scene and the U1 subway line was temporarily halted between 8.15pm and 8.45pm, although service has now resumed.
Patrick Maierhofer, a police spokesman, said in a statement that the male suspect was detained shortly after a 20-year-old man was brought to a hospital with life-threatening injuries.
Three members of a family were critically injured last night after an "out of control" man armed with a knife triggered a lockdown in central Vienna.
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In the first incident, a family of three were attacked. The police are trying to ascertain if the two attacks are related and carried out by the same person. "The three people were seriously injured and their lives are in danger", the spokesperson said, adding later that they were Austrian citizens.
The police said that a man has been arrested in the case but it yet not clear if the attacks were related.
No motive for the attack has been reported yet.