Three suicide attacks against offices in a Kurdish-controlled Iraqi town killed at least 40 people on Sunday, many of them Kurdish forces veterans volunteering to re-enlist, officials said.
The Islamic State jihadist group claimed the attack via affiliated Twitter accounts, saying the three suicide bombers were from Germany, Saudi Arabia and Turkey.
"At 10:30 this morning (0730 GMT), three car bombs struck Qara Tapah," said Mayor Wahab Ahmed, who was lightly wounded in the attack.
Other officials said there may have been only two car bombs and one suicide attacker detonating an explosives vest.
Qara Tapah lies close to Jalawla, a key battleground northeast of Baghdad between pro-government forces and IS jihadists.
The mayor said the explosions targeted his office, a building used by the Kurds' asayesh internal security service and an office of the Patriotic Union of Kurdistan party.
Ahmed said nearby buildings used by the electricity department and the Kurdish peshmerga forces' veterans affairs bureau were also seriously damaged in the explosions.
Kurdish officials said the attack killed a total of 40 people, many of them peshmerga veterans who had volunteered to return to active duty to fight IS.
"Twenty-four of the victims are peshmerga veterans," a senior Kurdish security official said, speaking on condition of anonymity because he is not authorised to talk to the press.
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"They had come to join the front against IS," he said.
The death toll rose through the day and security forces were still retrieving bodies from the debris as dusk fell.
Several dozen people were also wounded in the attack.
Twitter accounts affiliated with IS relayed a claim naming the three suicide bombers as Abu Sara al-Almani (German), Abu Mohammed al-Jazrawi (Saudi) and Abu Turab al-Turki (Turkish).
Confessionally and ethnically mixed Diyala province, which borders Iran, has seen intense fighting pitting militants of IS against Iraqi federal troops, and their Kurdish and Shiite militia allies.
In the provincial capital Baquba Sunday, a roadside bomb blast in a busy neighbourhood called Al-Dhabbat killed six civilians, a police captain and a doctor at Baquba hospital said.
It was not immediately clear who the explosion targeted.
Two women and a child were among those killed and several others were among the 10 people also wounded in the blast, the sources said.
A woman was killed and two children wounded when another bomb targeted a policeman's home in Baquba's Shifta neighbourhood, the same sources said.