BAGHDAD - Islamic State has published a video purporting to show the destruction from an airstrike on a bank in its northern Iraqi stronghold which the US-led coalition said had been aimed at disrupting the group's financing activities.

Reuters could not verify the authenticity of the footage posted by a news agency that supports the militant group, but two Mosul residents contacted by Reuters confirmed the location of al-Zuhour bank in an eastern district of the city.

Targeting Islamic State's finances is a key part of the coalition's strategy to defeat the group. Iraq's finance minister last year said the militants had looted nearly half a billion dollars from banks in Mosul and the other northern cities of Tikrit and Baiji after its lightning dash across the Syrian border in 2014.

Papers and burnt furniture littered the concrete and steel rubble of several buildings that appeared to have been destroyed by the bombing, the video showed. Debris hung from dust-covered tree limbs, and rescuers pulled an old man's bloodied body from the remains.

Footage from inside a damaged apartment building suggested civilian areas had also been hit. A military spokesman said earlier on Monday that a US aircraft had bombed an Islamic State cash distribution site which was distributing money to fund "terrorist" activities.

CNN, citing unnamed US defence officials, had said the building was destroyed by two 2,000-pound bombs. The officials could not say exactly how much money was there or in what currency, but one described it as "millions," CNN reported.

Islamic State, which split off from al Qaeda, has also financed its operations through oil smuggling, racketeering, kidnapping and taxing the millions of people living in areas it controls in Syria and Iraq.

At least seven mosques and dozens of shops in eastern Iraq were firebombed on Tuesday, security sources and local officials said, a day after 23 people were killed there in two blasts claimed by Islamic State.

Ten people were also shot and killed in Muqdadiya, 80 km northeast of Baghdad, security and hospital sources said. At least two mosques south of Baghdad were attacked last week after a Shia cleric was executed in Saudi Arabia, triggering angry reactions in Iraq and neighbouring Iran.

At the height of Iraq's civil war nearly a decade ago, such mosque attacks often unleashed revenge killings and counter attacks across the country.

Officials tried on Tuesday to head off further violence, condemning the mosque attacks as well as Monday's bombings which Islamic State said had targeted Shias.

Abdul Lateef al-Himayim, head of Iraq's government body overseeing Sunni religious sites, called them "a desperate attempt to destroy Iraqi unity", while the United Nations warned in a statement the mosque bombings could "take the country back into the dark days of sectarian strife".

Haqqi al-Jabouri, a member of the local council in Diyala province where Muqdadiya is located, said both types of attacks hurt the social fabric of the community. He blamed "undisciplined militias" for burning the mosques.

Meanwhile, gunmen shot dead two Iraqi television journalists north of Baghdad on Tuesday who had been on a reporting trip with a top security officer, the channel said.

Iraq is one of the most dangerous countries in the world for journalists, especially those from the country, who are far more exposed to attacks than their foreign counterparts.

"Armed militias assassinated correspondent Saif Tallal and his cameraman Hassan al-Anbaki near Baquba," the capital of Diyala province, a Sharqiya news presenter said on the air.

The journalists were killed while returning to Baquba from a reporting trip with Staff Lieutenant General Mizher al-Azzawi, the head of security command responsible for the province, the channel said.

The two were on their way back from the Muqdadiyah area, a security spokesman said.

Twin bombings in Muqdadiyah killed 20 people at a cafe the night before, and attackers subsequently blew up multiple Sunni mosques and burned houses and shops, officers said.

The United Nations issued a statement condemning the mosque bombings.

"Once again, places of worship are being attacked. The perpetrators want to incite sectarian violence, in a desperate attempt to take the country back into the dark days of sectarian strife," UN Iraq representative Jan Kubis said.

Iraq declared victory over the Islamic State militant group in Diyala early last year.

But the province remains a hotbed of violence by both the militants and powerful Shia militia forces that have played a major role in the fight against IS.

IS overran large areas north and west of Baghdad in June 2014, but Iraqi forces backed by US-led air strikes have since dealt the militants significant defeats.

Militant gunmen and bombers killed at least 12 people in a busy market area of Baghdad while a double blast at a cafe north of the Iraqi capital claimed another 20 lives.

An attack claimed by the Islamic State group and involving suicide explosions, gunfights and hostage-taking wreaked chaos in the eastern neighbourhood of Baghdad al-Jadida.