KHARTOUM, March 13 (Reuters) - Sudan rejected U.S. criticism of its human rights record on Thursday, saying George W. Bush's administration was the biggest rights abuser in the world and had ignored big improvements made by Khartoum.

The U.S. State Department said Sudan's record remained "horrific" with "continued reports of extrajudicial killings, torture, beatings, and rape by government security forces and their proxy militia in Darfur" in a report published on Tuesday.

But Sudan's Ministry of Foreign Affairs accused Washington of ignoring significant improvements in the human rights situation.

The "Sudan government has never hesitated in adopting legal procedure against the persons who committed human rights violations in Darfur," said the statement, released on the state Suna news agency on Thursday.

International experts estimate 200,000 people have died and 2.5 million been forced to flee homes in Sudan's western Darfur region since conflict erupted there in 2003. Khartoum puts the death toll at 9,000.

Sudan accused the United States of hypocrisy over the rights report, citing Guantanamo Bay, the Abu Ghraib prison scandal in Iraq and the suppression of "racial and religious minorities and the Muslims" in the United States as examples of U.S. abuses.

A Ministry of Foreign Affairs spokesman declined to comment on the call from British Prime Minister Gordon Brown on Wednesday for tougher sanctions against Sudan, saying officials still had to discuss it. (Writing by Andrew Heavens; Editing by Matthew Tostevin)