The attack was carried out about by four suicide bombers and took place on the day when hundreds of thousands of Shia Muslims gathered in Baghdad to commemorate a revered imam.
At least three policemen were killed on Sunday in a suicide attack south of Mosul, the northern Iraqi city where Daesh is fighting off a US-backed offensive, security sources said.
A group of about 10 assailants, including four suicide bombers, had tried to infiltrate a Federal Police helicopter base in al Areej, a police captain told Reuters.
Three policemen and three of the assailants were killed in the attack, he said. Police gave chase but the assailants managed to escape, he said.
Daesh is now besieged in the northwestern part of Mosul. Its Grand al Nuri Mosque is where the group's leader, Abu Bakr al Baghdadi, declared a "caliphate" over parts of Iraq and Syria in mid-2014.
The seventh imam
The attack came as hundreds of thousands of Shia Muslims thronged the mausoleum of Imam Kadhim in Baghdad for the climax of a week-long pilgrimage that saw millions converge on the Iraqi capital.
Kadhim, the seventh of 12 revered imams in Shia Islam, died in 799 AD. The commemoration has in recent years turned into a huge event that brings the Iraqi capital to a standstill for days.
"This visit means a lot to us, it is about showing respect for the suffering of the imam and the injustice he faced and about reaffirming our dedication to him," Ahmad Jamal, a 28-year-old civil servant in the crowd of pilgrims, said.
Shia religious events and sites are considered prime potential targets for suicide attacks by Daesh and huge security deployments were visible across Baghdad.