Police have cordoned off Matipo St in Whanganui as homes are searched in relation to a gang shooting.

Police have taken "a number of people" into custody as the investigation into a slain Mongrel Mob member hots up.

Kevin "Kastro" Ratana, 27, was killed at a Puriri St, Whanganui, home last Tuesday morning in a shooting, believed to be an attack by rival gang members Black Power.

On Monday evening police confirmed "a number of people" were arrested and taken into custody and charges could be laid.

Police cordons were on Monday blocking the road in Matipo St, Castlecliff, which is two streets away from the house where Ratana was killed.

SUPPLIED Whanganui Mongrel Mob member Kevin Ratana was shot and killed last Tuesday at a Whanganui house.

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Police confirmed the searches were related to the shooting and said several properties were being searched throughout Whanganui.

Detective Inspector Ross McKay said some of those in custody were expected to be released on bail, while others wouldn't as "potential charges are confirmed".

"Police also today recovered a number of firearms, firearms parts, and ammunition," McKay said.

"The Whanganui community can expect to continue to see an increased number of armed police, investigative staff, and the Eagle helicopter in the area as we work on the investigation.

"The main search area today was adjacent to a local primary school. Police used the opportunity to visit the primary school with the Eagle helicopter and speak with the pupils there, to offer reassurance."

The armed offenders squad was at the scene earlier on Monday and police were going in and out of two houses on the street.

MURRAY WILSON/STUFF Hundreds of mourners are gathering at the Parikino marae and urupā, north of Whanganui, to farewell slain gang member Kevin "Kastro" Ratana.

One house has a Black Power flag flying from the roof, and Black Power members were seen in the street watching police.

Hundreds of Mongrel Mob gang members flooded into the city for Ratana's funeral at a marae north of Whanganui.

Inspector Mark Harrison said there could be tension in the city overnight and gang members had been fortifying their properties and covering fences so people could not see into their properties.

"We know from experience when there is gang versus gang violence there is always a time of gangs building up or protecting themselves so it's not out of the normal and it's part of the reason we have additional resources in town."

MURRAY WILSON/STUFF Inspector Mark Harrison's press conference in Whanganui

Harrison said police had no information to suggest anything would happen, but the police helicopter was in town and it could get to any area in the city within 30 seconds.

"If something does happen we are able to respond."

McKay said last week both Ratana and the group that carried out the attack were "known" to police.

McKay believed more than one person was involved in the shooting.

Extra police were brought in from Manawatū and Whanganui to help with the search, and help secure the scene while forensic evidence was gathered.