* Ali Kushayb charged by global court in 2007
* Khartoum says investigated militia leader
* Violence has picked up in Darfur since January
KHARTOUM, June 3 (Reuters) - A Sudanese pro-government militia leader wanted for war crimes by the International Criminal Court took part in a raid on a rival tribe in the strife-torn Darfur region in April, Human Rights Watch said on Monday.
Conflict has raged through the western territory since mainly non-Arab tribes took up arms against the Khartoum government in 2004, accusing it of political and economic neglect.
Sudan mobilised troops and armed Arab militias, so-called Janjaweed, against the insurgents unleashing a campaign that has killed hundreds of thousands of people, according to activists and the United Nations. Sudan denies the charge and puts the death toll at 10,000.
Human Rights Watch (HRW) said several witnesses had identified Arab militia leader Muhammad Ali Abdel-Rahman, also known as Ali Kushayb, during an attack on a tribe in central Darfur in April.
"Witnesses placed Kushayb at the scene of an attack on the town of Abu Jeradil, 30 kilometers south of Um Dukhun, on April 8, riding in a government vehicle," HRW said in a report.
The attackers arrived in the town inhabited by a rival tribe in a convoy of government-issued Land Cruiser jeeps and carried anti-aircraft guns, rocket-propelled grenades and other army weapons, it said.
Abdel-Rahman was charged with carrying out war crimes in Darfur by the ICC in 2007. Prosecutors said he commanded thousands of Janjaweed militia and personally led attacks on towns and villages.
The global court later issued arrest warrants for Sudan's President Omar Hassan al-Bashir and other senior officials, accusing them of orchestrating the violence.
Sudan has insisted it is carrying out its own investigation into Abdel-Rahman and has said in the past it was holding him in detention - though rights activists have called the legal procedures a sham.
The Khartoum government has refused to deal with the ICC, saying its charges are part of a Western plot.
A spokesman for the international peacekeeping force in Darfur, UNAMID, confirmed fighting took place during that period in the area, which borders Chad. It had no other details.
The Sudanese foreign and justice ministries could not immediately be reached for comment.
Violence in Darfur has ebbed from 2004 peaks but fighting has picked up again since January as some Arab tribes, which the government has failed to disarm during several botched peace accords, have turned their guns on each other.
Around 300,000 people have been displaced across Darfur in fighting between the army, rebels and rival tribes since January, the U.N. humanitarian chief said last month. (Reporting by Ulf Laessing and Khalid Abdelaziz; Editing by Andrew Heavens)