At least nine of the Iraqi finance minister's guards are being held on terrorism charges, officials said on Friday after the minister demanded the premier's resignation following their arrest.

The dispute threatens to reignite a long-running feud between the secular, Sunni-backed Iraqiya bloc, of which Finance Minister Rafa al-Essawi is a member, and Shiite Prime Minister Nuri al-Maliki.

Higher Judicial Council spokesman Abdelsattar Bayraqdar told AFP that nine of Essawi's guards were detained under the anti-terrorism law, and that all the necessary arrest warrants had been obtained.

And he told Iraqiya state television that the commander of the guards had confessed to carrying out "terrorist acts," which he said meant "bombings and assassinations."

Maliki in an emailed statement put the number of guards arrested at 10, and expressed "astonishment" at what he termed "linking the issue of the detainees with political disputes" and "trying to pull the whole country toward sectarian strife."

He also denied that the arrests were sectarian in nature, saying that "carrying out judicial orders against accused (people) does not mean targeting a specific sect."

The interior ministry website said its forces arrested 10 guards around Essawi's house, and published what it said were copies of the warrants.

Essawi said on Thursday that a "militia force" -- an apparent reference to a security forces unit -- raided the ministry and his home "in an illegal act, without a judicial order," detaining 150 guards.

"I call on the prime minister to resign, because he did not behave like a man of state," Essawi told a news conference alongside parliament speaker Osama al-Nujaifi and Deputy Prime Minister Saleh al-Mutlak, also Iraqiya members.

A statement from Maliki's office on Friday, meanwhile, said without elaborating that some security forces members "did not act professionally" during arrests the day before, apparently referring to the arrest of Essawi's guards, and that the premier ordered them to be referred to the judiciary.

About 500 people protested against the arrests and Maliki on Friday in Ramadi, west of Baghdad, and several hundred also took to the streets of Samarra and Tikrit, north of the capital.

Iraqiya and other members of Maliki's unstable national unity government have accused him in the past year of concentrating power in his hands and moving towards dictatorship.

Opposition to Maliki escalated into calls for his removal, but his opponents lacked the parliamentary votes to do so. Essawi also 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.

An arrest warrant was also issued for Hashemi, like Essawi, an Iraqiya member, who fled to Iraq's autonomous Kurdistan region and eventually to Turkey, saying the charges against him were politically motivated.

Hashemi has since been given multiple death sentences in absentia on charges including murder, while death sentences have been handed down to his guards as well.