Baghdad - Four Islamic State group suicide bombers infiltrated an army headquarters west of Baghdad, killing an Iraqi general and five other soldiers, army and police officers said on Tuesday.

The bombers attacked a regimental headquarters in the Haditha area of Anbar province late on Monday, killing Staff Brigadier General Ali Aboud, Lieutenant Colonel Farhan Ibrahim and four others, the sources said. Major General Ali Ibrahim Daboun, the head of the Al-Jazeera Operations Command, said one suicide bomber blew himself up inside Aboud's office, while the other three detonated explosives elsewhere inside the headquarters.

Seven soldiers were also wounded in the attack, Daboun said. Colonel Faruq al-Jughaifi, the Haditha police chief, confirmed the attack, saying it took place near a major dam in the area, and that the bombers were dressed in military uniforms.

IS overran swathes of Iraq, including large parts of Anbar, in a sweeping offensive launched in June 2014, but has largely been on the defensive in the province since the middle of last year.

Iraqi tribesmen and security personnel defending Haditha, which lies near the country's second largest dam, have held off IS for more than 18 months with the help of air strikes by a US-led coalition.

The war with IS has taken a heavy toll on senior Iraqi officers in Anbar. Two heads of the Anbar Operations Command were wounded in 2015, while the commanders of a division and a brigade were killed in Anbar in April of that year. The province's governor was wounded in 2014.

Senior army and police commanders have also been killed in other provinces.

Meanwhile, thousands of Iraqi security personnel launched an operation on Tuesday aimed at retaking areas north of Baghdad from the Islamic State militant group, officials said. Counter-terrorism forces, soldiers, police and allied paramilitaries are taking part in the operation, which is backed by artillery and both Iraqi and US-led coalition aircraft, the Joint Operations Command announced.

An Iraqi army colonel said that more than 7,000 security personnel would take part in the operation, which the operations command said aims to retake areas west of the city of Samarra.

The targeted areas, which the colonel said extend from the city of Samarra up to the town of Baiji, are a corridor linking IS-held territory around the northern city of Mosul, the militants' main hub in Iraq, with areas farther south.

IS launched a devastating offensive in June 2014 that overran swathes of territory north and west of Baghdad, but Iraqi forces backed by US-led strikes have succeeded in regaining significant ground from the militants.

Iraqi forces retook Ramadi, the capital of Anbar, from the militants at the end of last year, and are now turning their attention to areas to the north through which IS has moved supplies and fighters to the province.