Two extremely valuable paintings stolen from a Parnell gallery could be held for ransom.

The portraits of Maori leaders by artist Gottfried Lindauer were stolen yesterday in a ram-raid on the International Art Centre in Auckland.

The works of art, which Lindauer painted in 1884, are worth between $350,000 and $400,000 each. They are known as "Chieftainess Ngatai-Raure" and "Chief Ngatai-Raure".

READ MORE: Million-dollar art heist: Interpol on watch for thieves

Auckland University Art History lecturer Ngarino Ellis said they would be difficult to sell here or overseas.

She says with a ransom, the criminal doesn't have to find a buyer.

"But they have never generally been very successful, because normally they nab the criminal at the point they hand over the money."

The painter's international reputation has recently been bolstered - Ms Ellis said a major travelling show of his works has just visited Europe.

"It's been over in the Czech Republic, at Pilsen, it was also over in Berlin and it was really well celebrated over there - they got record numbers into the exhibition."

Ms Ellis said it's also possible the paintings were stolen for personal pleasure, by someone who wanted to keep the work for themselves.

Police investigating the robbery said they wanted to hear from anybody who was in Parnell between 3.30am and 4am or anyone who may have information about where the paintings are.

They asked anyone with information to contact Auckland police on 09 302 6832, or Crimestoppers anonymously on 0800 555 111.