World Bulletin/News Desk
Iraqi government forces had stopped people at checkpoints and prevented them fleeing Mosul as ISIL militants took it over, he said. Now ISIL was using its own checkpoints to hunt down anyone associated with the Iraqi government.
"The full extent of civilian casualties is not yet known but reports received by UNAMI, the U.N. mission in Iraq, to this point suggest that the number of people killed in recent days may run into the hundreds and the number of wounded is said to be approaching 1,000," he told a news briefing in Geneva.
UNAMI has its own network of contacts and had interviewed some of the 500,000 who fled Mosul, he said. A further 40,000 people were estimated to have fled from Tikrit and Samara, according to the International Organization for Migration.
"There was also the execution of a court employee in the Dawasa area in central Mosul and the execution of 12 people in Dawasa who were believed to have been serving with the Iraq security services or possibly with members of the police."
The "great majority" of the militants were Iraqis, Colville said, citing UNAMI reports.
Prisoners released by the militants from Mosul prison had been looking to exact revenge on those responsible for their incarceration and some went to Tikrit and killed seven former prison officers there, Colville said.
"We've also had reports suggesting that government forces have also committed excesses, in particular the shelling of civilian areas on 6 and 8 June in Mosul, resulting in a large number of civilian casualties," he said.
"There are claims that up to 30 civilians may have been killed during this shelling," he said.
"We also received reports that government forces were at one point not allowing people to leave from Mosul as they tried to do so and people were actually being turned back from checkpoints on the outskirts of the city."
ISIL pause in Syria
The Syria branch of the Islamic State in Iraq and the Levant (ISIL) has put fighting on hold in Syria while it brings in weapons seized inside neighbouring Iraq, a monitoring group that tracks the violence said on Friday.
ISIL has battled rival rebel groups in Syria for months and clashed occasionally with President Bashar al-Assad's forces.
But its fighters appear to hold back in Syria this week, especially in their eastern stronghold near the Iraqi border, while their Iraqi wing was making rapid military gains.
Rami Abdulrahman, head of the Syrian Observatory for Human Rights, said that ISIL may have negotiated a truce with rival rebel brigades in Syria, although it was still laying siege to parts of the eastern city of Deir al-Zor, where Assad's forces and Nusra Front rebels are also dug in.
"(ISIL) has not being fighting for four days. We don't know why exactly. There is only some fighting northeast of Aleppo," Abdulrahman told Reuters by telephone.
Clashes between other rebel groups and government forces continued across Syria's civil war fronts, he said.
He said that ISIL have moved weapons into eastern Syria.
"Our people saw weapons on the road in Syria," he said.
Photos posted on social media by ISIL supporters also appear to show military equipment, including American Humvee patrol cars, being moved.
Reuters cannot confirm they were taken into Syria but the supporters say they were driven across the frontier.
Matthew Henman, Head of IHS Jane's Terrorism and Insurgency Centre, said in a report that ISIL's capture of Iraqi territory along the Syrian border will give the group greater freedom of movement of men and materiel across the two countries.
ISIL gained more ground in Iraq overnight, moving into two towns in the eastern province of Diyala, while U.S. President Barack Obama considered military strikes to halt their lightning advance.
Syria's civil war started with pro-democracy street rallies in 2011 but turned into an armed insurgency after a military crackdown on civilian protesters. Hardline factions like ISIL have gathered strength in the conflict, which has killed 160,000 people and displaced millions of people.