US Secretary of State makes unannounced visit to Iraq

He will "underscore our strong support for the Iraqi government as it addresses significant security, economic, and political challenges," Kirby said.

Kerry, who is visiting Iraq for the first time since September 2014, will "discuss the coalition's continued support for Iraqi-led efforts against" IS, Kirby said.

The unannounced visit to Iraq follows the US official's first trip to Bahrain as Secretary of State on Thursday, where he discussed political developments in the region - including the war on Yemen, Syria as well as Bahrain's human rights record.

Kerry also sent a strong message to Iran, suggesting it should should help end wars in Yemen and Syria.

Kerry called on Iran to "help us end the war in Yemen... help us end the war in Syria, not intensify, and help us to be able to change the dynamics of this region".

Tehran should "prove to the world that it wants to be a constructive member of the international community and contribute to peace and stability", Kerry told a news conference in Manama.

The US is involved in several fighting fronts across the region.

In Iraq, an international anti-IS coalition led by the United States is providing strategic intelligence and on-the-ground training for forces fighting the militants.

Iraqi government forces and Sunni Arab tribal fighters breached IS defences in the town of Hit, in Anbar province, on Thursday, but the first phase of the operation to re-take IS' Iraq stronghold in Mosul appears to have stalled.

The fierce fighting in Hit raised fears for the safety of civilians trapped in the crossfire as the two-week offensive reached the stage of street battles as Iraqi troops fought to clear IS from the city, street by street, with the US air force providing aerial support.

Iraqi security sources in Anbar said they had established refugee camps to house civilians evacuated during the army's progress in the area, but multiple sources in Hit told The New Arab that thousands had been trapped in the town for days.

Civilian casualties as a result of airstrikes have been also reported by activists, who said coalition and Iraqi warplanes were sparing no part of the city.

"Iraqi forces are using a scorched earth policy against [IS], who were also preventing civilians from leaving," said Mohammad al-Anbari, a local official in Hit.

Anbari claimed the Iraqi media was deliberately ignoring civilian casualties in the town.

Meanwhile, in Yemen, US-supplied bombs were allegedly used in a Saudi-led coalition airstrike on a market that killed at least 97 civilians including children last month, according to Human Rights Watch.

Kerry's visit comes just weeks before President Barack Obama is scheduled to attend a Gulf Cooperation Council summit in Riyadh, where Washington's foreign policy in the region is expected to be discussed with Gulf leaders.