Iraqi authorities said Thursday they arrested a politician belonging to the party of Vice President Tareq al-Hashemi, who is at the centre of a row after he was charged with running death squads.
The warrant against Hashemi, who denies the accusations, came shortly after US forces completed their withdrawal from Iraq and has pitted the Shiite-led government against the main Sunni-backed bloc, stoking sectarian tensions.
Riyadh al-Adhadh, deputy chief of Baghdad provincial council, was arrested while on his way to work on Wednesday in connection with funding insurgent groups, officials said.
"An insurgent group confessed that he is funding them and giving them orders," a Baghdad security official told AFP on condition of anonymity.
Adhadh is a member of the Iraqi Islamic Party, a Sunni grouping that belongs to the broader Iraqiya coalition to which Hashemi belongs. Hashemi is a former leader of the IIP but has since split from the party.
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The IIP confirmed the arrest, but condemned it as "an unprecedented escalation" and called for Adhadh to be freed.
Iraqiya has largely boycotted parliament and cabinet in response to what it claims are Prime Minister Nuri al-Maliki's centralisation of power, and has called on the premier to respect a year-old power-sharing deal or quit.
The bloc won the most seats in March 2010 elections, but was outmanoeuvred by Maliki's alliance, which eventually formed the government after a prolonged impasse was finally broken in November of that year.
The row with Maliki erupted last month when authorities charged Hashemi and Maliki, a Shiite, said his Sunni deputy Saleh al-Mutlak should be fired after the latter said the premier was "worse than Saddam Hussein".
Hashemi has been holed up in the autonomous Kurdish region for the duration of the crisis, and Kurdish officials have so far declined to hand him over to Baghdad.
On Tuesday, Iraq's cabinet clamped down on Iraqiya's boycotting ministers by decreeing they could not run their ministries while staying away from its meetings.
The United Nations and the United States have urged calm but their calls for talks involving all of Iraq's political leaders have so far gone unheeded.