Dec 22 (Reuters) - U.S. oil giant ConocoPhillips on Friday gave the financial greenlight to its $8 billion Willow oil and gas drilling project in Alaska.

"With this project authorization, we've begun winter construction," said chief executive Ryan Lance.

Environmental and indigenous groups in November had asked a federal court in Alaska to temporarily bar ConocoPhillips from going forward with construction of the project in the state's Arctic, arguing a stay is necessary to stop imminent cultural and environmental harms.

The groups had filed two lawsuits challenging the project's approvals shortly after they were issued.

(Reporting by Tanay Dhumal in Bengaluru; Editing by Shounak Dasgupta and Krishna Chandra Eluri)