Iraqi security forces backed by Shi'ite militias on Sunday broke the two-month siege of Amerli by Islamic State militants and entered the northern town, officials said, according to The Associated Press.

The mayor of Amerli and army officers said troops backed by militias defeated fighters from the Islamic State to the east of the town. Fighting continued to the north of Amerli in several villages, the AP reported.

"Security forces and militia fighters are inside Amerli now after breaking the siege and that will definitely relieve the suffering of residents," said Adel al-Bayati, mayor of Amerli, according to the AP.

It was hailed as a huge strategic victory for the Iraqi security forces and the militia fighters who joined them after a summer that saw the Islamic State lead other Sunni armed groups in seizing almost one-third of the country's territory, the AP reported.

"Amerli's battle is a golden victory registered by the Iraqi security forces who are still fighting the terrorist groups in north and south areas of Amerli," said military spokesman Qassim al-Attta, according to the AP.

Atta described Amerli as a launching pad to retake the northern province of Salahuddin, including its capital, which was captured by IS in June, the AP reported.

"The next step will be holding the ground tightly and liberating all the areas which link Amerli to Salahuddin," Atta said on state television, according to the AP. "Our forces will gather in thousands in Amerli to march towards Tikrit."

While Kurdish fighters, backed by US air strikes, had beat back the Islamic State after losing terrain in August, the collection of Shi'ite security forces and militias had yet to score a significant military win, the AP reported.

The advance of the Iraqi forces in Amerli comes after the U.S. military carried out air strikes overnight on IS militant positions near the town and airdropped humanitarian supplies to the trapped residents there, according to the AP. More aid was dropped from British, French and Australian planes.

The Pentagon said the warplanes hit three Humvee patrol vehicles, a tank and an armed vehicle held by militants in addition to a checkpoint controlled by the group, according to the military's Central Command, which runs U.S. operations in the Middle East, the AP reported.