Image copyright REUTERS/Antara Foto/Risyal Hidayat Image caption The birds were kept inside bottles to keep them from flapping, customs officials say

Police in Indonesia have arrested a man they suspect was smuggling rare birds inside plastic bottles.

The man was allegedly caught carrying the live birds on a passenger ship near the city of Surabaya.

They included 21 yellow-crested cockatoos, which are listed as endangered. They were kept inside bottles to stop them from flapping.

The birds are known to sell through legal channels for as much as £1,000 ($1,500) each.

Customs officials said the haul also included an unspecified number of green parrots.

Image copyright REUTERS/Antara Foto/Risyal Hidayat Image caption The number of yellow-crested cockatoos in the wild has dropped due to smuggling

The exact number of yellow-crested cockatoos in the wild is not known, but the International Union for Conservation of Nature place it on their critically-endangered list.

Birdlife, a nature conservation group, say the birds' numbers are dropping due to " unsustainable trapping for the cagebird trade".

In 2013, two Indonesian military employees were given a warning after they were found to be running a bird-smuggling ring on board a military aircraft.

Bags containing rare birds were found when the plane refuelled in Australia.