Vienna, Nov 6 (TIWN) Austria's Interior Minister Karl Nehammer has admitted that a warning from Slovakia last summer about a gunman who went on the rampage in the centre of Vienna was not followed up.

Four people were fatally shot and 23 others wounded on Monday night.

Police in Slovakia revealed they had tipped off Austrian authorities about "suspects from Austria" trying to buy ammunition in July.

Reports suggest the trip to buy bullets failed as the gunman had no licence.

It has also emerged he was released early from a jail sentence last December for trying to join jihadists in Syria.

According to German media, the 20-year-old, who was shot dead by police nine minutes after the attack began, travelled to neighbouring Slovakia to buy ammunition for a Kalashnikov AK-47 assault rifle but returned empty-handed.

Slovak police said they had informed their Austrian colleagues immediately, adding they would not comment further.