Iraqi Prime Minister Nuri al-Maliki's spokesman said the deadly attack on Sunday may be linked to the bloody civil war in neighboring Syria, where foreign-backed militants have battled Kurdish forces.
A senior Kurdish security official said two militants opened fire at the headquarters of the "asayesh" security service in Arbil, then entered and blew themselves up.
An explosives-rigged ambulance also detonated at the scene, the official said on condition of anonymity.
Kurdistan region health minister Raykot Hama Rashid told journalists that six asayesh members were killed and more than 60 people wounded in the attack.
An AFP journalist heard three blasts in Arbil, and heavy gunfire. Smoke could be seen rising in the air, as ambulances raced to the scene.
While much of Iraq is plagued by near-daily violence that kills hundreds of people each month, the three-province Kurdistan region in the country's north has largely been spared the deadly unrest.
Sunday's blasts were the first to hit Arbil since May 2007, when a truck bomb exploded near the same asayesh headquarters, killing 14 people and wounding more than 80.
"Syria has affected all of us," the Iraqi premier's spokesman Ali Mussawi told AFP, adding that the attacks may be "one of the offshoots of the Syrian crisis."
Iraqi security analyst Ali al-Haidari agreed.
"The attack is linked to the differences between the Kurds and al-Nusra Front," Haidari said, referring to the terrorist group that operates in Syria.
"Today's attack is al-Nusra Front's revenge against the Kurds inside Kurdistan," he said.
Iraq's autonomous Kurdish region has become increasingly embroiled in the bloody conflict raging across the border in Syria.
Clashes last month between Kurdish forces and militants seeking to secure a land corridor connecting them to Iraq pushed tens of thousands of Syrian Kurds across the border, seeking refuge in Iraqi Kurdistan.
Region president Massud Barzani has threatened to intervene in the Syrian conflict to protect Kurdish civilians, although officials have since backtracked on those remarks.
The blasts came a day after results were announced for the region's parliamentary elections, which saw an opposition movement in second place ahead of Iraqi President Jalal Talabani's party.
Iraqi Kurdistan enjoys a high level of autonomy from Baghdad, and the regional parliament has passed laws on a wide range of issues. The Kurdish region also operates its own security forces and visa regime.
HH/HH