Australia Thursday approved a controversial Indian-backed project to build one of the world's biggest coal mines, two months after a court blocked the development over its impact on two vulnerable reptiles.

The Queensland state project, which environmentalists fear threatens the World Heritage-listed Great Barrier Reef, was approved subject to "36 of the strictest conditions in Australian history", Environment Minister Greg Hunt said in a statement.

Adani, which is in the fifth year of development and approvals for the huge project, welcomed the decision and the "rigorous and painstaking conditions".