The assailants, a minority ethnic group called Shabak, took over the entry checkpoint into the Christian-dominated town of Bartilla, about 28 miles north of Mosul, and tore down Christmas decorations in the Assyrian market, reported Assyrian International News Agency (AINA).
Witnesses say they also harassed a Christian procession headed toward St Mary church, throwing rocks at the group.
Around 100 armed Shabaks later tried to enter St Mary Church but church guards reportedly blocked them from entering, leading to a conflict and an exchange of gunfire that left four Christians wounded.
Assyrians in Bartilla, who are unarmed, fear more attacks against their community in the near future.
According to AINA, Christians in Bartilla say they did not provoke the attack and have in the past worked with Shabaks to advocate for the rights of ethnic minorities in Iraq.
The Shabak assailants are residents of Bartilla and were said to have been led by Hassan Ganjou, who is allegedly a former member of the Mahdi Army (JAM) and the Islamic Supreme Council of Iraq, and now works as a security guard for a Shabak parliament member.
The attack in Bartilla followed a church bombing at St Thomas Church in Mosul on last Wednesday that killed two men and wounded five others.
Since 2003, more than 200 Christians have been killed in Iraq, and since June 2004, some 65 churches have been attacked or bombed, including 40 in Baghdad, 19 in Mosul, five in Kirkuk, and one in Ramadi.
Human rights groups such as Hudson Institute's Center for Religious Freedom have criticised the Iraqi government for not doing enough to protect the country’s Christian minority.
The UN High Commission for Refugees estimates that since 2003, some 250,000 to 500,000 Christians have left the country, which translates to about half the Christian population leaving within six years.