“I announce from here the end and the failure and the collapse of the terrorist state of falsehood and terrorism which the terrorist Daesh announced from Mosul,” Haider al-Abadi said in a speech shown on state television on Monday, using an Arabic acronym for Islamic State.

A 100,000-strong alliance of Iraqi government units, Kurdish Peshmerga fighters and Shi’ite militias launched the offensive to recapture the northern city in October.

Abadi, who arrived in Mosul on Sunday, thanked troops and the coalition. But he warned more challenges lay ahead, before raising the Iraqi flag.

Iraq declared a week-long holiday to mark the victory, while people celebrated in Iraqi streets.

The stench of corpses along Mosul’s streets was a reminder of the gruelling urban warfare required to dislodge IS.

Much of the city of 1.5 million has been destroyed, its centuries-old stone buildings flattened. One of IS’s last acts was to blow up the historic al-Nuri mosque and its famous leaning minaret.

Thousands of people have been killed. The United Nations says 920,000 civilians have fled their homes during the campaign. Close to 700,000 people are still displaced.

The coalition said in a statement Iraqi forces were in “firm control” of Mosul, but some areas still needed to be cleared of explosive devices and possible IS fighters in hiding.

IS released a statement claiming to have mounted an attack on Iraqi forces in Mosul. Reuters could not immediately verify the report.

Abadi had been meeting officials in Mosul amid celebration which contrasts with the fear that spread after a few hundred IS militants seized the city and the Iraqi army crumbled in July 2014.

IS leader Abu Bakr al-Baghdadi shocked world powers three years ago by appearing at the pulpit of Mosul’s Grand al-Nuri Mosque to declare the caliphate and himself the leader of the world’s Muslims.

A reign of terror followed which eventually alienated even those Sunni Muslims who had supported IS as allies against Iraq’s Shi’ite majority.

In the aftermath of victory in Mosul, Abadi’s government faces the task of managing the sectarian tensions there and elsewhere that enabled IS to win support, and the threat of a wave of revenge violence in the city.

US President Donald Trump congratulated Iraq and said IS’s days were numbered. Secretary of State Rex Tillerson called the victory “a critical milestone” in the war against IS.

Baghdadi has fled the city and his whereabouts are unknown.

– Reuters