CANBERRA, Feb. 18 (Xinhua) -- Drought and excessive water use have been found responsible for the deaths of millions of fish in an Australian river.

The Australian Academy of Science on Monday released its report into three major fish kills in New South Wales' Darling River in December 2018 and January 2019.

The report, which was compiled at the request of the opposition Australian Labor Party (ALP), found that millions of fish died in a 40-km stretch of the river near Menindee, 1,000 km west of Sydney.

"The conditions leading to this event are an interaction between a severe (but not unprecedented) drought and, more significantly, excess upstream diversion of water for irrigation," it said.

Craig Moritz, chair of the report panel and director of the Center for Biodiversity Analysis at Australian National University, warned that "the Darling will die" unless urgent steps were taken.

"Our review of the fish kills found there isn't enough water in the Darling system to avoid catastrophic outcomes," he told reporters.

"No one expects the river to run every year but they have cut the water so hard, the river is dying," he said.

Acknowledging the report, ALP leader Bill Shorten described it as "startling" but said it presented an opportunity to accept the current water management plan was not working.

A separate panel appointed by the governing Liberal-National party coalition is expected to deliver its own report into the incidents on Wednesday.