(CNN) Police said four people were injured Wednesday in two separate knife attacks about 30 minutes apart in central Vienna, Austria.

Three victims were injured in the first attack outside a restaurant near the Nestroyplatz subway station, a police spokesman told CNN. The victims were a couple and their daughter, CNN affiliate ORF reported.

The fourth victim was injured in the second attack at Praterstern, a major city square, the spokesman said. Authorities are investigating whether the incidents are linked, the spokesman said.

An "Afghan male" was arrested in connection with the attack in Praterstern, Vienna police spokesman Patrick Maierhofer told CNN. The suspect stabbed a Chechen national, causing life-threatening injuries, Maierhofer said.

It was not clear if the suspect was connected to the first stabbing, Maierhofer added. He said police continue to investigate the stabbings with the help of surveillance videos and eyewitnesses.

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