With President Jalal Talabani being treated in Germany after a stroke, Iraq is without a key mediator as a new political crisis brews between the secular Sunni-backed Iraqiya bloc and the Shiite premier.

Talabani's stroke may in itself spark turmoil -- his resignation or death could cause a protracted dispute over his successor.

The 79-year-old has sought to bring together feuding politicians, Sunni and Shiite Muslims, Arabs and Kurds, during political crises that have plagued Iraq in the past year.

After Prime Minister Nuri al-Maliki said on Friday that 10 of Finance Minister Rafa al-Essawi's guards were arrested the previous day for alleged terrorism offences, Talabani's mediation skills will be sorely missed.

Essawi, a Sunni member of Iraqiya, told a news conference a "militia force" raided the ministry and his home "in an illegal act, without a judicial order," and called on Maliki to quit "because he did not behave like a man of state."

He spoke to journalists alongside parliament speaker Osama al-Nujaifi and Deputy Prime Minister Saleh al-Mutlak, fellow members of the main Sunni-backed parliamentary bloc.

Maliki expressed "astonishment" at "linking the issue of the detainees with political disputes" and "trying to pull the whole country toward sectarian strife."

But a later statement from his office said some security force members "did not act professionally" during arrests made on Thursday, in an apparent admission of misconduct.

Iraqiya and other members of Maliki's unstable national unity government have accused him of concentrating power in his own hands and moving towards a dictatorship, leading to calls for him to be removed from office.

Maliki's opponents ultimately lacked the parliamentary votes to remove him, but Essawi called on Thursday for no-confidence proceedings to be reopened.

The arrest of Essawi's guards comes almost exactly a year after Sunni Vice President Tareq al-Hashemi's guards were arrested and accused of terrorism.

Hashemi himself -- like Essawi, an Iraqiya member -- eventually took refuge in Turkey and has since been given multiple death sentences for charges including murder, as have some of his guards.

Talabani, a Kurd, was hospitalised on Monday after suffering a stroke, and was airlifted to Germany on Thursday for specialist treatment.

"While on paper (Talabani's) role is somewhat limited, his influence and mediation skills have gone a long way in smoothing over the country's troubled political scene," said John Drake, an analyst with AKE Group.

"Some may describe his position as 'ceremonial' but he has made it a lot more active, simply though dialogue and discussion, which play a strong role in Iraqi politics."

Should Talabani require replacing, choosing a successor would probably be drawn out , contentious and messy.

"If Talabani were no longer president... we would likely see a lot of negotiation between different political players, not just over the simple act of replacing him, but over the terms and conditions of selecting an approved candidate," said Drake.

"If an ethnic Kurd is to be selected, political groups affiliated with other communities in the country may only allow it if concessions are made elsewhere. The discussions could last weeks, if not months."

Under Iraq's constitution, the vice president takes over if the presidency becomes vacant, and a new president must be elected by parliament within 30 days.

Vice President Khudayr al-Khuzaie, who is filling in for the president as he undergoes treatment, would take charge temporarily if Talabani stands down or dies.