Iraq's new government plans to intensify efforts to uproot cells of the Islamic State extremist group and introduce "robust measures" to achieve sustainable security throughout the country, the country's U.N. envoy said Tuesday.

Jan Kubis told the U.N. Security Council there are almost daily reports of the arrest or elimination of the militant group's "terrorists, their leaders, sleeper cells and hideouts."

Iraq declared victory over IS last year, but the group continues to carry out scattered attacks, particularly in the north. The extremists have lost virtually all the territory they once ruled in Syria and Iraq, but still control small, remote pockets in eastern Syria along the border.

Kubis said most IS movements in recent months have been to the western border with Syria and Iraq has responded by deploying thousands of troops on its side. But he said the group, also known as Daesh, remains active in other Iraqi provinces as well, notably Kirkuk, Salah ad Din and Diyala.

Earlier this month, U.N. investigators reported discovering at least 202 mass graves in Iraq containing between 6,000 and 12,000 bodies believed to be victims of atrocities by IS during its three-year reign

Kubis said the U.N. political mission in Iraq "continues to advocate for justice and accountability for international crimes," and he told the council the head of a U.N. investigative team promoting accountability for IS crimes, Karim Khan, arrived in Iraq on Oct. 30.

Kubis, who is stepping down in January after almost four years, said the particularly difficult period he served as U.N. envoy "has against all odds and skepticism ended well, with a promising future prospect for the country and our role in assisting it."

He pointed to the recent formation of a new government with veteran Kurdish politician Barham Salih as president and independent Shiite politician and former vice president Adel Abdul-Mahdi as prime minister.

The new government's program outlines "specific plans for reforms, investment, and for transitioning Iraq from a crisis content to sustainable development" and recommends steps to tackle corruption in all sectors, Kubis said.

The government also "intends to introduce robust measures to further improve and achieve sustainable security throughout the country, intensifying efforts to uproot Daesh terrorist cells to counter this insurgency," he said.