KHARTOUM, July 21 (AFP) -- Thirty-eight men were killed when rebels in west Sudan's Darfur region attacked a relief convoy and had a gunbattle with military escorts, a media service and an official statement said Wednesday.

The Sudanese Media Center and the humanitarian affairs ministry said the incident occurred on Monday at Ambru in North Darfur, part of a region where fighting since February last year has triggered a major humanitarian crisis.

In a statement, the ministry denounced the attack, which it said was the second one to be made on an Ambru relief convoy. It made no mention of fighting or casualties.

SMC reported that nine government soldiers and 29 rebels were killed in the gunbattle.

The government said it had lodged a complaint against the rebels with the African Union's ceasefire monitoring committee based in Al-Fashir. The attack brought to 109 the number of violations of last April's ceasefire by the rebels.

SMC said that in a separate incident, rebels on Monday attacked a truck chartered by the UN World Food Programme in North Darfur, unloaded and took away the food it was was carrying and then allowed the driver to drive on after beating him.

The government meanwhile announced that due to the onset of the rainy season, some parts of Darfur, including Gineina, have become inaccessible and that relief could no longer be delivered by trucks.

State Humanitarian Affairs Minister Mohamed Yusuf Abdallah was Wednesday quoted by the official Al Anbaa daily as saying an airlift has already begun to those parts and if this did not work the alternative of airdropping supplies would be introduced.

Abdallah said other areas such as Al-Fashir in North Darfur and Nyala in South Darfur were not affected by the rains because they had a railway and asphalted roads.

In another development, the University of Nyala was closed down indefinitely following clashes between student factions in which 12 students have been injured and taken to hospital, the independent Al Ayam daily said Wednesday.

Al Ayam, reporting from the South Darfur capital, said the university administration on Tuesday announced the suspension of studies after clashes the previous day between students of the ruling National Congress party and those in opposition parties during a campaign for elections of the student union.

The students battled each other with bamboo sticks and iron bars, the paper said.