The PGA Tour has filed a federal civil lawsuit against LIV Golf's financial backers, Saudi Arabia's Public Investment Fund and governor Yasir Othman Al-Rumayyan, per filings in Manhattan.

The complaint, filed under seal in the US District Court for the Southern District of New York, is the latest move in the bitter war between golf's leading organisation and its breakaway opponent.

It follows the PGA Tour filing a counter-suit against LIV Golf last month, levelling accusations of interference in player contracts.

More than 30 players have been suspended from competing on the tour since their defection, while US players have been excluded from Ryder Cup consideration.

A number of players previously filed a federal antitrust lawsuit against the PGA Tour, though several – including six-time major champion Phil Mickelson – have been asked to be removed from that action.

Al-Rumayyan is also the chairman of Premier League outfit Newcastle United and heads up Saudi-owned petroleum company Saudi Aramco.