UPDATE 2-Bombs, Attacks Hit Iraqi Cities, at Least 50 Dead

* At least 37 killed in twin blasts in Kut

* Other deadly attacks in Tikrit, Najaf, Diyala (Recasts with further attacks, adds official comment)

By Ahmed Rasheed and Khalid al-Ansary

BAGHDAD, Aug 15 (Reuters) - Suicide attackers and car bombs struck cities across Iraq on Monday, killing at least 50 people and wounding scores more in a rash of apparently coordinated assaults carried out by affiliates of al Qaeda, authorities said.

In the worst attack, a roadside bomb followed by a car bomb targeting police killed at least 37 people in Kut, a mainly Shi'ite Muslim city 150 km (95 miles) southeast of the capital Baghdad, police and health officials said.

Dhiyauddin Jalil, a director of local provincial health department, said more than 68 people were wounded in the Kut blasts and doctors in the city's main hospital said they were struggling to treat casualties, many with severe burns.

"These attacks... are trying to influence the security situation and undermine confidence in the security forces," said Major General Qassim al-Moussawi, a spokesman for Baghdad security operations, blaming al Qaeda-linked groups.

Violence in Iraq has subsided dramatically since the height of sectarian slaughter in 2006-07. But militants are increasingly testing local security forces as the last American troops prepare to withdraw by an end-of-year deadline.

Kut had been relatively quiet since August last year when a suicide bomber killed 30 policemen and destroyed a police station as the U.S. military ended combat operations in Iraq.

Dozens more were killed or wounded on Monday in bombings and attacks in other cities, puncturing the relative calm of the Muslim holy month of Ramadan.

At least eight people were killed and 14 wounded when a suicide car bomber attacked a municipality building in Khan Bani Saad, about 30 km (20 miles) northeast of Baghdad, in the province of Diyala, two police sources said on Monday.

Two suicide bombers attacked an Iraqi counter-terrorism unit in Tikrit, 150 km (95 miles) north of Baghdad, killing at least two policemen and wounding six in a failed attempt to free al Qaeda prisoners, a police official said.

One attacker detonated his suicide vest hoping to kill a high-ranking counter-terrorism officer, and the other was shot dead during the attack, said Captain Jassim al-Jibouri, an officer with the Tikrit counter terrorism unit.

In the southern holy Shi'ite city of Najaf, at least three people were killed and 19 more wounded when two car bombs exploded, authorities said. Police captain Hadi al-Najafi in Najaf said the bombs targeted a police building.

"There was a roll call for the police in the early morning. The first killed and wounded policemen and as the ambulances came the second car exploded," said Mussab Mohammad, a local resident who witnessed the attacks.

Another man was killed and 12 people were wounded in simultaneous car and motorbike bombings in the centre of the northeastern city of Kirkuk, police sources said.

In al-Wajehiya, another town in Diyala province, a bomb in a parked car went off near a government building, killing one policeman and wounded 13, a police source said.

U.S. soldiers are scheduled to leave by the end of the year, more than eight years after the U.S. invasion that toppled Saddam Hussein. But Iraqi and U.S. officials are discussing whether some stay on as trainers after 2011. (Additional reporting by Muhanad Mohammed in Baghdad,; Aref Mohammed in Basra, Khaled Farhan in Najaf; Writing by Patrick Markey; Editing by Mark Heinrich)