UPDATED 5.15PM: The Prime Minister says the security scares at Parliament today, which closed off streets around the building, are disturbing.

Someone drove a ute baring a message for John Key onto the Parliamentary forecourt and set off a flare in the cab, delaying Bill English's arrival at the Budget media lockup.

He'd apparently claimed there were 600 litres of petrol in a tank on the deck of the ute, which he was going to explode.

John Key said that's worrying.

"I think it's reasonably distressing that you can get somebody drive onto the forecourt, with the limited information I have, with a car that potentially could have been used as some sort of explosive device. Parliamentary security I think will have to go away and look at that."

The man was arrested and is still in custody.

This has shown up on the forecourt of parliament and it looks like the person driving it was just arrested pic.twitter.com/VqVn9NQAec

— Jacinda Ardern (@jacindaardern) May 25, 2016

What's going on at Parliament? Security told me bomb scare? pic.twitter.com/3qi5fki69U

— Jenna Raeburn (@JennaRaeburn) May 26, 2016

Bomb dog has arrived. Watching from @FoxMarama's office pic.twitter.com/eD4B6514xh

— Seǝn Gillespie (@SeanDG) May 26, 2016

Later, a second security threat was made, which caused the area behind Parliament to be cordoned off and access was blocked.

Police attended the second incident and gave few details.