"Two suspects, believed to have been involved in the incident, were arrested," Gambari told reporters following a meeting with Sudanese Foreign Ministry Undersecretary Mutrif Siddiq in Khartoum Thursday.
"This is a positive development that will serve stability in Darfur and help UNAMID perform its tasks," he added.
He said it is important to bring the suspects to trial, saying that "they should be tried at once, which will send a strong message that assaulting the peacekeepers is not be tolerated."
"We are a neutral party and we are working for the interest of the Darfur people," he added.
Unidentified gunmen Tuesday ambushed a UNAMID police convoy near Nyala, capital of South Darfur State, leaving seven peacekeepers wounded, two of them were in serious condition.
About 22 UNAMID personnel have been killed in similar attacks against the mission patrols since it has taken over the peacekeeping task in the region.
UNAMID took over the peacekeeping mission in Darfur from the African Union Mission in Sudan (AMIS) on Dec. 31, 2007.