A power outage has knocked out electricity to Parliament in Wellington.

More than 12,000 people are affected by the power cut, which was caused by a "zone sub outage" according to Wellington Electricity.

It's understood the power is out at Parliament, the Wellington courts and the train station.

Wellington Electricity's outage site shows it is spread over multiple suburbs, and that power is expected to be restored within three hours.

There has been a power outage in Wellington Station. Services are unaffected however ticket window purchases are cash only.

— Metlink Wellington (@metlinkwgtn) August 3, 2018

The outage happened about 12.15pm.

A Twitter user shared a photo on the site, saying, "Power outage in Wellington CBD. In unrelated news there's a lot of smoke pouring out of the Beehive."

People commenting on the post said the smoke was Parliament's back-up diesel generators kicking in.

Power outage in Wellington CBD. In unrelated news there’s a lot of smoke pouring out of the Beehive pic.twitter.com/cSa081rL5G

— Marama Paki (@cowsdad) August 3, 2018

Power cut in central Wellington... in related news I do not recommend being stuck in a lift during a power outage. V glad for cellphones with torches and colleagues with calming personalities. Twas a long 5 minutes #takingthestairs

— Clea Marshall (@speakingclealy) August 3, 2018