Bystander allegedly stabbed while making citizen's arrest in Melbourne CBD

A man has been taken into custody after one person was injured during an alleged stabbing at a shopping centre carpark in Melbourne's CBD.

Police allege a man armed with a knife was seen acting "erratically" as he ran through a carpark on Lonsdale Street about 6am today.

Two bystanders gave chase along Elizabeth Street and made a citizen's arrest near the intersection of Lonsdale Street.

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A 32-year-old Dallas man was arrested by police shortly atfter.

One witness, 41, involved in the citizen's arrest sustained a stab wound.

He was taken to hospital with a non-life-threatening injury to his lower body.

The second man, 35, was not injured in the scuffle.

No charges have been laid.

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Anyone who witnessed the incident is urged to contact police or Crime Stoppers.

There has been an increased presence across the city following an alleged stabbing on Little Bourke Street last month.

The Public Order Response Team (PORT) have increased patrols in Melbourne since the incident, police said.

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