Dunedin Lorde fans camp out ahead of NZ tour opener

Some of Lorde's biggest fans have been camped out at the Dunedin Town Hall since 5:30am on Tuesday ahead of her concert tonight marking the start of her New Zealand tour which is also her birthday.

The pop sensation turns 21 today and a group of around 25 lined up outside the venue - some with flowers they'd bought with their own pocket money - hoping to catch a glimpse of the 'Royals' hitmaker.

Security is expecting big crowds and will be putting up barriers for the sell-out show.

"I've been here since 5:30am, I'm a huge fan of Lorde and I really wanted to come," student Beth Moody says.

"I'd really like to be at the front and to be able to see her and support her."

The small crowd is spending the afternoon singing some of Lorde's hit songs and "getting pumped" for the concert.

"I feel like the New Zealand shows are always a little bit more special and I think this will make it even more special the fact that she is spending her birthday putting on a show," fan Josie Moon says.

Lorde will also play shows in Christchurch, Wellington and Auckland later this week.