Police manned checkpoints, patrolled churches and residential areas in Mosul - a city considered by US and Iraqi commanders to be Iraq's most dangerous and last stronghold of Al-Qaeda.
Jaweat Ismael, chief of the city's bureau of displaced people, said there was "no new wave of displacements" on Monday after the police reinforcement, according to Agence France-Presse.
This past week, some 3,000 Christians fled Mosul and took refuge in churches, monasteries and homes of relatives in nearby Christian villages and towns after more than a dozen Christians were murdered in Mosul within the last two weeks.
"The Christians were subjected to abduction attempts and paid ransom, but now they are subjected to a killing campaign," explained Duraid Mohammed Kashmoula, the governor of northern Iraq's Ninevah province, according to The Associated Press.
Iraqi Prime Minister Nuri al-Maliki ordered on Sunday an investigation of all the attacks, and vowed to do all that he can to protect the vulnerable community.
Meanwhile, UN special representative Staffan de Mistura expressed concern about the rise in violence directed at the Christian community in Mosul.
"Staffan de Mistura strongly condemned the killing of civilians and expressed his concern at the spike in violence that has targeted the Christian communities in recent days, particularly in and around Iraq's northern city of Mosul," read the UN statement, released on Monday.
Since the US-led Iraq war in 2003, more than 200 Christians have been killed, dozens of churches bombed, and more than half the Iraqi Christian population has left the country.
Last week, three Christians were murdered within 24 hours in Mosul.
"Iraq's minorities have historically been, and remain an integral part of the country and its social fabric, enriching both its culture and politics," UN's de Mistura said. "Respecting and guaranteeing the political and legal rights of minorities in Iraq is fundamental to a stable and democratic future for the country."