A Colac police detective said the crime investigation unit was called to reports of a serious assault in Apollo Bay's McLachlan Street on Saturday about 10.15pm.

It is alleged a man slashed with a knife in what is believed to be a dispute over drugs.

The police spokesman alleged a 34-year-old Apollo Bay man seriously assaulted a 58-year-old male victim in an incident which left him with wounds to his head.

He alleged a 34-year-old Apollo Bay man assaulted another man, causing injuries to his hands.

He said the victim was transported to Geelong Hospital for medical treatment, which he said would be "ongoing".

The dispute happened in a driveway, the men are known to each other and an investigation into the exact motivation behind the assault is still being conducted.

The arrested man is expected to be charged with serious assault-related offences, be remanded in custody overnight Sunday and appear in the Geelong court for a bail/remand hearing on Monday.

Anyone with information about the assault is requested to contact the Colac police station or Crime Stoppers on 1800 333 000.

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