The ISIS terrorist group, which claimed responsibility for an ax attack on board a train in Wurzburg, Germany, has released a video of the attacker pledging allegiance to the jihadist group.

In the footage released by ISIS's al-Amaq propaganda outlet, 17-year-old Afghan national Mohammed Riyad can be seen delivering a speech in the Pashto language, while brandishing a knife.

He is described in the video as "a soldier of the Islamic State who carried out the Wurzburg attack."

18 people were wounded in the knife and ax attack, before the terrorist was shot dead while attempting to charge police responders.

In the video, Riyad declares his intent to "slaughter infidels".

Police investigating the attack - which left two people in critical condition - discovered an ISIS flag in the attacker's bedroom.

The Afghan national had arrived in Germany last year as a refugee, part of a massive influx of largely Muslim migrants and refugees that year.

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