Malaysia announced during the weekend that Bashir is to take part in an economic forum in its country next week.
"Malaysia should not turn itself into a port of call for fugitives from international justice," Donna Guest, deputy Asia Pacific director at Amnesty International, said in a statement. "The Malaysian government should bar al-Bashir from its territory and arrest him if he turns up."
U.N. Security Council Resolution 1593 in 2005 referred Sudan to the International Criminal Court after evidence emerged of serious rights violations in Darfur.
Bashir is accused of genocide, war crimes and crimes against humanity. Khartoum isn't party to the Rome Statute that created the international court, however.
Luis Moreno-Ocampo, the chief prosecutor at the ICC, told the Security Council that Bashir "has learned how to continue to commit crimes" and act in defiance of the United Nations.
Bashir returned to Khartoum from Ethiopia where he was engaged in multilateral talks over various conflicts in Sudan. Skirmishes along the de facto border between Sudan and South Sudan, which gains independence in July, threaten to unravel a 2005 peace deal.
A U.S. State Department official told reporters during a background briefing that U.S. officials didn't have contact with Bashir during the talks in Addis Ababa.