(AFP) -- Iraqi police said they found a Christian shopkeeper shot to death in the restive northern city of Mosul on Saturday, the fifth Christian killing in a week thought to be related to March elections.

Adnan al-Dahan, a 57-year-old Syrian Orthodox, was found with bullet wounds to his head in the northern Mosul district of al-Belladiyat, police and his relatives said.

Dahan had been kidnapped from his grocery shop last week in the neighbourhood of Al-Habda, also in northern Mosul, according to a police officer who did not want to be named.

"He was kidnapped last week from his shop but we did not reveal this publicly because we were trying to get him back by paying a ransom," one of Dahan's relatives said, speaking on condition of anonymity.

Dahan was the fifth Christian to have been killed during the past week in Mosul, which is located about 350 kilometres (220 miles) north of Baghdad and has a Christian population of between 2,000 and 3,000.

Local leaders had expressed concern Christians could be targeted ahead of the March 7 parliamentary election in a country wracked by sectarian violence since the US-led invasion of 2003.

In November, Human Rights Watch warned minorities in the oil-rich north including Christians were the collateral victims of a conflict between Arabs and Kurds over who controls Iraq's disputed northern provinces.

On Wednesday, 20-year-old Assyrian Christian student Wissam George's bullet-riddled body was recovered after he went missing the same morning.

A day earlier, a gunman killed 21-year-old engineering student Zia Toma and wounded 22-year-old pharmacy student Ramsin Shmael, both Assyrian Christians.

Greengrocer Fatukhi Munir was gunned down inside his shop in a drive-by shooting late on Monday, and armed assailants killed Rayan Salem Elias, a Chaldean, outside his home on Sunday.

In late 2008, a systematic campaign of killings and targeted violence killed 40 Christians and saw more than 12,000 flee Mosul.