Civilians return to their village after it was liberated from Islamic State militants, south of Mosul, Iraq October 21, 2016.Reuters

A 20-year-old man in Iraq wants to avenge the death of his four brothers and abduction of his five sisters by the Islamic State group (Isis). Younis Ali's brothers were shot dead in a village near Mosul when they resisted being used as human shields. His sisters were also abducted by the jihadist group. 

Hundreds more faced the same fate as Ali's brothers on Thursday and Friday, when the terrorist group rounded up 284 men and boys as human shields against Iraqi and Kurdish forces. The deceased didn't even receive a proper burial. They were dumped in a mass grave shovelled by a bull dozer at Mosul's defunct College of Agriculture, a source told CNN.

"All I want to do is find people from Daesh and behead them," he said.

The young man is a member of a tribal group that is fighting with government forces against IS militants in their last stronghold and Iraq's second largest city. 

On Friday, Zeid Ra'ad Al Hussein, UN High Commissioner for Human Rights, expressed his concern over the situation in Mosul. 

"We are gravely worried by reports that (Isis) is using civilians in and around Mosul as human shields as the Iraqi forces advance, keeping civilians close to their offices or places where fighters are located, which may result in civilian casualties," he said. 

"There is a grave danger that (Isis) fighters will not only use such vulnerable people as human shields but may opt to kill them rather than see them liberated," he said.

The United Nations on Friday had said that 550 families from villages around Mosul were taken hostage by Isis. Two hundred families from Samalia village and 350 families from Najafia have reportedly been taken into Mosul to prevent them from fleeing. 

Zeid said that the commission has evidence that Isis not only forced the villagers to head to Mosul, but also that those suspected of disloyalty were shot dead. 

Meanwhile, at least 30 Isis militants are believed to be holed up inside security buildings in Kirkuk, southeast of Mosul.