The 85-page report, based on government documents, said Bashir aides involved in Darfour included military commanders as well members of the regime-backed Janjaweed militia.
The report was prepared for the International Criminal Court. In March 2005, the United Nations Security Council was assigned to indict individuals responsible for the abuses, Middle East Newsline reported. So far, no indictments have been issued.
"The Sudanese government at the highest levels is responsible for widespread and systematic abuses in Darfour," the report said. "The Sudanese government's systematic attacks on civilians in Darfour have been accompanied by a policy of impunity for all those responsible for the crimes."
An estimated 300,000 people were killed in Darfour since 2003. More than 1.2 million Darfour residents have been driven from their homes, with many of them fleeing to neighboring Chad.
Entitled "Entrenching Impunity: Government Responsibility for International Crimes in Darfour," the report said Bashir used Janjaweed as part of a government campaign to drive two million people from their homes. Janjaweed members were drafted into Sudanese security forces and paid from the loot of raided villages.
The report said Bashir played a leading role in the offensive in Darfour. Human Rights Watch quoted a commander as ordering soldiers to attack civilians.
"Joint government-militia offensives were well-coordinated," the report said. "The looting was not random; it was clearly organized and premeditated. In many cases, it appears to have been organized by the military commander and conducted in a methodical way. The troops and Janjaweed used in attacks south of and around Kutum were told that they could keep their looted goods if they 'fight well.'"
The report detailed battles in which the Sudanese Air Force provided close air support for Janjaweed and army strikes on villages in Darfour. Several pilots were said to have requested transfers to avoid missions that targeted civilians. One pilot who refused attack orders was arrested.
HRW has called for a UN investigation of Bashir and his aides. The aides included Vice President Ali Osman Taha, regarded as instrumental in negotiating the end of the civil war in the south in 2004.
"Frequent allegations have been made that Vice President Ali Osman Taha is the key government policymaker where Darfour is concerned -- and that he was one of the primary instigators of the policy of militia recruitment and use," the report said.
The report said Taha arranged for the release from prison of Janjaweed leader Mussa Hilal in 2003. Hilal was identified as deputy commander of a Sudanese force that targeted Darfour rebels and non-Arab villages.