* Suicide bomb kills 16 civilians in Balad
* Merged Iraq-Syria al Qaeda group claims recent attacks
* Bomb explodes near school northeast of Baghdad (Releads with new attacks, adds details)
By Sylvia Westall
BAGHDAD, Aug 12 (Reuters) - At least 16 people were killed and 41 wounded on Monday in a suicide bomb attack on a crowded cafe in Balad, 80 km (50 miles) north of Baghdad, part of the worst wave of violence in Iraq in around five years.
Two roadside bombs - one planted near a playground and another near a school - also killed six people and wounded dozens, some of them children, in the town of Muqdadiya, 80 km northeast of the capital.
Those blasts underlined a shift in tactics by suspected Islamist militants, who are increasingly targeting not only military checkpoints and marketplaces, but also cafes and recreational areas used by families and children.
The latest bloodshed came as al Qaeda claimed responsibility for weekend bombings across Iraq which killed dozens of people during Eid al-Fitr, the festive end to the Muslim fasting month of Ramadan, heightening fears of even wider sectarian slaughter.
The Islamic State of Iraq and the Levant (ISIL), formed earlier this year through a merger of al Qaeda's affiliates in Syria and Iraq, said on jihadist forums it was behind the attacks across Baghdad and southern provinces on Saturday.
It also warned the government to stop arresting suspected militants or face more violence.
"The Islamic State deployed some of its security efforts in Baghdad and the southern province and other places to deliver a quick message," ISIL said, according to the SITE Monitoring group, which tracks jihadist websites.
Bombs ripped through markets, shopping streets and parks late on Saturday as Iraqi families were out celebrating Eid. Nearly 80 people were killed and scores wounded, police and medical sources said.
It has been one of the deadliest Ramadan holidays in years in Iraq, where Sunni Islamist militants are waging an insurgency against the Shi'ite-led government.
July had the highest monthly death toll from attacks since 2008, with more than 1,000 Iraqis killed, according to United Nations statistics.
The renewed violence prompted a statement from Washington condemning the attacks and offering to work closely with Baghdad to confront al Qaeda and other groups.
The worst single incident on Monday occurred in Balad, where mayor Maliki Laftah told Reuters that all of the casualties were civilians.
In a separate attack near the city of Mosul, 390 km (240 miles) north of Baghdad, gunmen intercepted a car carrying three soldiers who were on their way to join their unit and shot them dead, police said.
It was not immediately clear who was behind Monday's violence, although suspicion is likely to fall on ISIL.
The group, which has also claimed responsibility for jail breaks in Iraq last month in which hundreds of convicts escaped, said a government campaign to arrest suspects and ramp up security in the capital had only made things worse.
"They will pay a high price for what they did, and they will not be secure day or night during Eid or other times," the ISIL statement said, according to the SITE translation.
"They should watch their footsteps and stop the detention campaigns and cease harming the Sunni clans, and ... expect more of what will harm them and what will bring them to their senses."
The Interior Ministry, which said last month it was facing an "open war", said on Sunday that media reports about the attacks had been exaggerated and that its recent security crackdown had been effective. (Additional reporting by Ziyad al-Sanjari in Mosul, a Reuters reporter in Baquba, Ghazwan Hassan in Tikrit and Suadad al-Salhy in Baghdad; Writing by Sylvia Westall; Editing by Mike Collett-White)