Authorities: 11 soldiers in Iraq killed by Islamic State

11 soldiers were killed in an overnight attack by the Islamic State group against a base in eastern Iraq, authorities said Friday, in the jihadists' deadliest operation in the country this year.

The extremist Sunni group took over large swathes of Iraq and neighbouring Syria in 2014, declaring itself a new "caliphate" for Muslims, before Baghdad declared victory in late 2017 after a grinding national campaign.

But a low-level insurgency by the jihadists has persisted, flaring up at various points, especially in rural areas north of Baghdad around the city of Kirkuk, and in the eastern provinces of Diyala and Salaheddin.

In a further sign of its resilience, IS also on Friday attacked a prison in Syria, killing at least 18 Kurdish security forces and prison guards, while losing at least 16 of it own fighters, according to the Syrian Observatory for Human Rights monitor.

A senior military official based in Iraq's Diyala province said "eleven soldiers, have been killed during an attack carried out by the Islamic State" against a military base.

The attack took place around 2:30 am (2330 GMT) on Friday in the Hawi al-Azim area, the source added, on condition of anonymity.

Diyala province governor Muthanna al-Tamimi confirmed the death toll, according to the Iraqi News Agency.

But he also hit out at the Iraqi army, alleging they were caught unprepared.

"The base is fortified. There is a thermal camera, night vision goggles and a concrete watch-tower," he said.

"The terrorists exploited the cold and the negligence of the soldiers," he alleged, adding that the attackers then escaped to the neighbouring province of Salaheddin.

'Poor training'

Since the Iraqi government declared victory over IS in December 2017, the jihadists have waged a campaign that has seen them hit both military and civilian targets.

According to Iraqi analyst Imad Allou, IS "is trying to reorganise its fighters and activities in Iraq".

He pointed to "poor training" on the part of the Iraqi security forces, lack of follow-up by officials, as well as disregard of instructions and low temperatures as some of the reasons that the jihadists were able to stage the attack.

A UN report last year estimated that around 10,000 IS fighters remained active across Iraq and Syria, many of them in Kurdish-controlled areas.

The ongoing IS presence in Syria is largely in desert hideouts in the east of the country, where the Kurds maintain a semi-autonomous administration that borders Iraq.

On 3 December, at least nine Iraqi Kurdish Peshmerga fighters and three brothers were killed in attacks claimed by IS in the northern Iraqi village of Khidir Jija, just south of the Iraqi Kurdish capital Erbil.

Nine more Peshmerga fighters were killed in two other IS attacks in Iraq in late November and early December.

IS also claimed a bombing against a market in Sadr city, a Shia suburb of the capital Baghdad, that killed dozens of people in July last year.

Having relied on backing by a US-led military coalition to defeat IS in 2017, Iraq must largely depend on its own forces to fight the jihadists after the coalition ended its combat mission last year.

Coalition troops remain in the country, but their capacity is restricted to a training and advisory role.