An Australian zoo has posted an urgent plea on its Facebook page for help in returning eight stolen endangered monkeys, so small they could fit in a handbag or the palm of your hand.

Symbio Wildlife Park, south of Sydney, said thieves broke into the park on Sunday night and stole a breeding pair of Cotton top Tamarins, their two babies, and four Pygmy marmosets.

These animals are part of international breeding programmes and are crucial to the survival of the species, there are only 300 Cotton top Tamarins left in the wild, so time is running out, said the zoo's Facebook message.

These animals need specialized housing and diet to survive, if they are not returned home safely, they may not survive, the whole team at Symbio are extremely worried, it said.

If you have any information, or know someone who can, please email or call the park, everything will be treated anonymously, all we want is the animals home safe.

The zoo published photographs of the tiny monkeys.

Park director John Radnidge said the thieves cut power to the zoo and cut through three padlocks to gain access to the monkeys.

On a cold, wet, windy, miserable, rainy night they cut the power to the exhibit, it was very clear these people knew exactly what they were doing. They had probably cased the joint before the attack, Radnidge told local media on Tuesday.

Radnidge said there was no black market in Australia or Asia for the monkeys, unlike Australia's native birds and lizards.

Cotton-tops and pygmy marmosets are so rare and unusual, those who have them in their possession will be found, I'm sure of that, he said.

(Reporting by Michael Perry)