More than 400,000 people have been displaced from western Mosul some two months into the Iraqi army's battle against the Daesh terrorist group, according to the United Nations.

The U.N. Office for the Coordination of Humanitarian Affairs (OCHA) said - citing the Iraqi government - that 434,775 people have fled Daesh's last stronghold in Iraq since Iraqi forces launched the western Mosul operation on February 19.

This brings the number of internally displaced people, since the Mosul operation started in October, to a total of 615,150 Iraqis.

According to OCHA, about 30,000 civilians have returned to their homes in western Mosul since end-April - meaning that the number of internally displaced people from western Mosul stands at 403,490 people.

The U.N. Refugee Agency (UNHCR) announced on Tuesday the opening of a new camp in eastern Mosul for citizens displaced from the west. The newly opened Hasansham U2 camp has a capacity of 9,000.

While Iraq said the eastern part of Mosul was cleared of extremists in January, the offensive to regain the western part is thought to be more difficult because of the population density.

Seven months into the campaign to recapture Iraq's second largest city, government forces say it is now in its final phase after opening a new front in the northwest of Mosul last week and gaining ground in several districts there.

Iraqi forces began the country's biggest military operation in years on October 17 last year and recaptured the east side of the city in January. But an assault launched the following month on the part of Mosul that lies west of the Tigris river has seen a sharp rise in displacement. Mosul is divided by the Tigris River, and while the series of bridges crossing it have either been damaged or destroyed, they would provide a link between the Iraqi government-held east and Daesh-held west Mosul if they can be repaired or otherwise bridged.

Mosul is by far the largest city that had fallen to the militants in both countries. The density of the population is slowing the advance of Iraqi forces. Western Mosul contains the old city center, with its ancient souks, the Grand Mosque and most government administrative buildings. It was from the pulpit of the Grand Mosque that Daesh leader Abu Bakr al-Baghdadi declared a self-styled "caliphate" over parts of Syria and Iraq in 2014. The city, Iraq's second biggest, is the largest urban center captured by Daesh in both countries and its de facto capital in Iraq. Raqqa is its capital in Syria. Daesh was thought to have up to 6,000 militants in Mosul when the government's offensive started in mid-October. Of those, more than 1,000 have been killed, according to Iraqi estimates.