* Blast hits contested city of Kirkuk
* Attack follows suicide bomb attack on Sunni lawmaker
* Ethnic Kurds locked in dispute with Baghdad government.
By Mustafa Mahmoud
KIRKUK, Iraq, Jan 16 (Reuters) - A suicide bomber killed 15 people in Iraq's Kirkuk on Wednesday after detonating a explosives-packed truck outside a Kurdish party office in the city at the centre of a dispute between Baghdad and the country's autonomous Kurdistan.
Shoppers and police helped drag bloodied survivors out of the rubble and wrecked vehicles after the huge blast tore through a commercial street in Kirkuk, near the local headquarters of the Kurdistan Democratic Party or KDP.
The attack came as Iraq's Shi'ite Prime Minister Nuri al-Maliki is locked in a feud with ethnic Kurds in the north over disputed oilfields and also facing Sunni Muslim protesters in a western province calling for him to step down.
"A suicide bomber driving a truck packed with explosives detonated the vehicles outside the KDP headquarters. It's a crowded area, dozens were killed and wounded, Police Brigadier Sarhat Qadir told Reuters.
Local Kirkuk health officials and police said at least 15 people were killed and more than 100 were wounded.
Another three people died and 37 more were wounded in a separate bombing outside a rival Kurdish political party office in Tuz Khurmato, 170 km (105 miles) north of the capital.
The attacks came a day after a suicide bomber killed an influential Sunni Muslim lawmaker in the west of Iraq where thousands of Sunni protesters have been holding mass demonstrations against Maliki.
A year after the last U.S. troops left, Iraq's government of Sunni, Shi'ite and Kurdish parties is deadlocked in a crisis over how to share power, increasing worries that the OPEC country may slide back into wide-scale sectarian confrontation.
Sunni protesters have been camped out in western provinces for three weeks demanding reforms of laws they say the security forces use to unfairly target their minority community. Some are calling for Maliki to step down.
Many Sunnis believe the Shi'ite premier has amassed power at their expense, sideling their leaders from power-sharing. Shi'ite leaders point to key Sunni leaders in top government posts as proof power-sharing is genuine.
The political crisis has been complicated by the dispute between Baghdad's Arab-led central government and Kurdistan over control of oilfields and territory that is testing the country's uneasy federal union.