World powers and Iraq's top Shiite cleric, Grand Ayatollah Ali al-Sistani, had piled pressure on MPs to put aside their differences to help counter a major jihadist-led onslaught that has overrun swathes of territory north and west of Baghdad.
After two sessions in which they made no progress, MPs elected Salim al-Juburi parliament speaker, a post traditionally held by a Sunni Arab that must be filled before the process of forming a government can go ahead.
It was not immediately clear if his election was part of a package deal involving the two outstanding senior posts of president and prime minister, but Tuesday's progress after previous deadlocked sessions indicates that some type of accord has been reached.
Lawmakers must now elect a president, who will then give the biggest bloc the first chance to form a government.
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The UN's Iraq envoy, Nickolay Mladenov, has warned politicians that "failing to move forward on electing a new speaker, a new president and a new government risks plunging the country into chaos".
"Iraqi forces began a military operation to liberate the city of Tikrit and our forces were able to control the southern part of the city," Ahmed Abdullah Juburi, the governor of Salaheddin province, of which Tikrit is the capital, told AFP.
An army colonel said the police academy and a hospital had been retaken, and the governor confirmed they were back in government hands, along with the governorate headquarters.
Tribesmen and security forces also battled militants in the town of Dhuluiyah on Thursday, 80 kms north of Baghdad.
Violence also struck south of Baghdad today, with bombings in the Madain area killing nine people, including four soldiers, officials said.