Three days of major jihadist attacks around Iraq, including on a university, have left dozens dead in a stark display of militant strength and the country's enormous security challenges.

Militants assaulted the city of Samarra, battled security forces in Mosul, took hundreds of hostages at Anbar University in Ramadi and carried out numerous other attacks in Baghdad and elsewhere.

Iraq is suffering its worst violence in years, and with none of the myriad problems that contribute to the heightened unrest headed for quick resolutions, the bloodshed is likely to continue unabated.

Powerful jihadist group the Islamic State of Iraq and the Levant has been blamed for most of the latest attacks, and is believed to be responsible for much of the violence in the country.

"Evidently, ISIL is in a very strong position," said John Drake, a London-based security analyst at AKE Group. "It is able to stand its ground in open fighting with the national security forces, which is major."

And with even the United States having struggled to curb violence in the country, it will be even more challenging for Iraqi security forces, which have significant shortcomings in training and discipline.

"Militancy in the centre of the country was a major headache for the strongest military force in the world, so it's no wonder that the Iraqi security forces are encountering such difficulties," Drake said.

"They are facing a massive challenge."

- New generals, old tactics -

Kirk Sowell, the Amman-based publisher of the Inside Iraqi Politics newsletter, said the violence clearly shows that militants are "very strong".

But the question is why "they have maintained this strength... why are the Iraqi security forces not more capable of dealing with this?"

One issue is widespread arrest campaigns by security forces that Sowell said sweep up many people who are likely innocent, terming it a "completely ineffective security policy".

He also said the high rate of turnover among senior officers is problematic, noting that there have been five different top commanders in restive Anbar province in roughly two years.

"They keep recycling these generals... but there's no change in tactics, there's no evidence that they're learning," he said.

The latest large-scale attacks began Thursday morning, when militants travelling in dozens of vehicles, some mounted with anti-aircraft guns, attacked the city of Samarra, north of Baghdad, and occupied multiple areas.

They were only displaced after heavy house-to-house fighting and helicopter strikes, during which officials said 12 police and dozens of militants were killed.

The following day, heavy fighting broke out between security forces and militants in multiple areas of the northern city of Mosul, one of the most dangerous areas of the country.

The clashes and shelling, combined with other attacks in the surrounding Nineveh province, killed more than 100 people over two days.

And on Saturday, militants infiltrated Anbar University in Ramadi, west of Baghdad, killed its guards and took hundreds of students and staff hostage.

The attack prompted an assault by security forces that eventually freed the hostages but also led to an hours-long battle with militants.

While militants have attacked government buildings and taken hostages before, universities are not their usual target.

"The targeting of young civilians in violence is more emotive than attacks on the security forces," Drake said when asked about the university attack.

And later on Saturday, seven bombs ripped through different areas of the Iraqi capital, killing at least 25 people.

Iraq is plagued by myriad problems that contribute to the violence, from widespread anger among the country's Sunni Arab minority, long-running political paralysis, ineffective security forces and the bloody civil war in neighbouring Syria.

None of these issues are likely to be resolved soon.