Iraqi army helicopters have conducted airstrikes in the northern Kirkuk province, killing at least seven people and injuring 20 others, as the military pursued Islamic State fighters in the country's north, sources on the ground have told Al Jazeera.

The troops targeted several neighbourhoods in the city of Hawijah on Saturday. Among those who were killed were two women, who were hit when the government forces struck a maternity and children's wards of a hospital in the Sunni-dominated city south of Kirkuk.

It was not immediately clear if the other casualties were IS fighters or civilians, raising concerns that civilian deaths in Sunni communities could trigger a backlash against Shia-dominated government forces.

In the province of Nineveh, which includes the strategic city of Mosul, government forces led by Kurdish armed fighters had also reportedly killed six IS fighters as they recaptured four towns and villages on Friday.

Meanwhile, in the town of Sulaiman Bek, which was recaptured by government forces, soldiers have discovered a shallow grave with at least 15 bodies, according to Al Jazeera sources.

The mass burial site was found by Iraqi Kurdish forces and armed Shia volunteers, after retaking the town from the IS.

The bodies are believed to be Shia truck drivers, kidnapped three months ago by the IS. Each of the men had been shot in the head.

Volunteers working with the victims' families and local police are excavating the remains.

The government has been stepping up its operation against the IS, after the Sunni-armed group gained control of vast swathes of territories in Iraq and neighbouring Syria. They have been aided by Kurdish forces and armed Shia volunteers, as well as US air strikes.

Kurdish forces, however, complained that their operation against the IS has been hampered by the lack of arms and ammunition.

"The main problem is when the weapons and help are delivered through Baghdad there are difficulties because they will not be delivered so soon," Rozh Shawes, Kurdish Region Deputy Prime Minister, told Al Jazeera's Sue Turton.

"We here in Kurdistan are afraid that the policy is still the same and there will be attempts to keep the weapons in Baghdad and not to send to Kurdistan."

Strong message of support

In Baghdad, Iraqi Foreign Minister Hoshyar Zebari said on Saturday that US President Barack Obama's plan for an international anti-jihadist coalition was a "strong message of support" for Baghdad and its fight against the IS.

"We welcome that, and we have repeatedly called on our international partners for help and support because this threat is a very deadly threat...not only to the people of Iraq or the region, but to Europe, to America, to NATO," Zebari told AFP news agency.

"This is basically our fight. But we need the support, our capacity is limited, and we need the support to enhance our capacity," he said.

Obama outlined plans at a NATO summit on Friday for a broad coalition to defeat the IS, which led an offensive that overran chunks of five Iraqi provinces in June, and also holds significant territory in neighbouring Syria.

The initial IS drive swept Iraqi security forces aside, but the Iraqi government won its first major victories of the conflict in recent days, breaking a months-long siege of one town and retaking other territory from the rebels.