Two men have been critically injured in two separate incidents overnight. One was assaulted in a Christchurch Bar and the other was caught up in a fight in a Wellington area notorious for crime.

Wellington police were called to the corner of Taranaki and Dixon Sts around 4am to reports of disorder.

A group were seen fighting which resulted in one man being taken to hospital with critical injuries and three others, aged 21,23 and 28, being arrested and charged with fighting in a public place.

Just hours prior, a Christchurch man was taken to hospital in a critical condition after being assaulted in a bar on Hereford St.

A police spokesperson said the attacker had left the scene and was unable to be located.

This mornings incident in Wellington comes just days after a 48-year-old man was stabbed in the leg on the same street.

"The victim and his associate became involved in a prolonged argument with another small group outside the Wesley Methodist church on Taranaki St that resulted in the victim receiving a serious stab wound to the leg," Detective Senior Sergeant Tim Leitch said.

The male offender fled the scene while a passer-by provided lifesaving first aid to the injured man.

Wellington central has longed been plagued by crime which got so severe that council last year implemented Pōneke Promise - a social contract between the city's hospitality industry, retailers, police and councils to take collective action to address the safety issues in the CBD.

At the time, Police data revealed that the number of sexual assaults in Wellington increased by nearly 50 per cent in five years. The number of acts intended to cause injury, including common and serious assault, had also grown by 35 per cent over the same period.

Projects within the Pōneke Promise were incorporated into four themes: physical improvements, harm reduction, community spaces and places, and business confidence.

The solutions to fix the situation included moving a block of public toilets, new deep cleaning for some footpaths, extra CCTV cameras, an interim youth hub, and a new central community centre.

Behind the scenes, advanced gaming technology was used to create a large-scale visualisation of Wellington, like a digital twin that's fed by real-time data.