By Stephanie Nebehay

GENEVA (Reuters) - Sudan's government continues to launch deadly land and air attacks in Darfur, where peacekeepers lack the resources to protect civilians, a United Nations human rights investigator said on Tuesday.

Sima Samar, U.N. special rapporteur on human rights in Sudan, said all sides in the conflict were committing abuses, including looting and rapes, without being held responsible.

"In the period under review, there have been widespread allegations of arbitrary arrests and detention, torture, incommunicado detention and serious violations of the right to fair trial," Samar said in her latest annual report covering two visits to Sudan this year.

All perpetrators should be prosecuted in fair trials, she said in the report to the U.N. Human Rights Council that flagged violations in Darfur and the oil-rich Abyei region.

"There are several reports of air attacks by government forces, leading to extensive civilian casualties," the report said, citing bombings in west Darfur and in north Darfur in the first half of this year.

"The majority of the bombs apparently impacted on civilian populated areas, including detonations in the vicinity of water installations, a school and a market," it continued, adding that scores of people were killed and wounded.

Sudan carried out 21 aerial bombardments in Darfur in the first three weeks of July, killing as many as 12 people, including children, according to the independent investigator and former Afghan deputy prime minister.

"The air strikes were carried out by the government of Sudan with Antonov aircrafts and MIG fighter jets," she said.

Experts estimate 200,000 people have been killed and 2.5 million driven from their homes since mostly non-Arab rebels took up arms in early 2003 accusing Khartoum of neglect.

A joint U.N.-African Union peacekeeping force, known as UNAMID, has been deployed in Darfur after delays, but only has 9,990 soldiers and police out of an initially promised 26,000.

Many communities in Darfur have expressed concern at the perceived "inability of UNAMID to protect the civilian population from the conflict and incidents", Samar said.

She called for Khartoum and the international community to give their "unconditional support to speeding up and completing the deployment of UNAMID".

Concerns were mounting about "violations of civil and political rights in different parts of the country in the lead-up to the general elections" scheduled for 2009, she said.

She also raised concerns about 500 people, including activists and journalists, who disappeared after a rebel attack in Khartoum in May. The group is believed to be in detention where they may be subjected to torture, the report said.

Samar is to address the U.N. Human Rights Council on Monday. The 47-member forum renewed her mandate in December for another year, overcoming resistance from African and Islamic states.