Researchers in a remote jungle in Indonesia have discovered a giant rat - five times the size of a typical city rat - and a tiny possum that are apparently new to science.

Unearthing new species of mammals in the 21st century is very rare. The discoveries by a team of American and Indonesian scientists are being studied further to confirm their status.

The animals were found in the Foja mountains rainforest in eastern Papua province in a June expedition, said US-based Conservation International, which organised the trip along with the Indonesian Institute of Science.