A group of nearly 50 Indian nurses have been taken against their will by bus from a hospital in the militant-controlled city of Tikrit in Iraq, India's foreign ministry.

Foreign ministry spokesman Syed Akbaruddin declined to say who had taken the nurses, or where they were headed, but said the government had spoken with them shortly before they boarded the bus.

Asked about reports of an explosion near the hospital, he said was not aware of a blast, but that some nurses had been lightly injured by broken glass.

"In zones of conflict there is no free will," Akbaruddin told reporters at a briefing, when asked if the nurses had been kidnapped. "This is a situation where lives are at stake."

Tikrit, the birthplace of former President Saddam Hussein, has been the site of fierce fighting this week as Iraqi troops battle to regain control of the city from the Islamic State (IS).

A group of 40 construction workers were kidnapped in the northern Iraqi city of Mosul two weeks ago, and all but one of them are still in captivity.

30,000 Saudi troops deployed to Iraq border

Saudi Arabia has deployed 30,000 soldiers to its border with Iraq after Iraqi soldiers withdrew from the area, the Saudi-owned al-Arabiya television reported.

The world's top oil exporter shares an 800km border with Iraq, where Islamic State insurgents and other Sunni Muslim militant groups seized towns and cities in a lightning advance last month.

King Abdullah has ordered all necessary measures to protect the kingdom against potential "terrorist threats", state news agency SPA reported.

The Dubai-based al-Arabiya said on its website that Saudi troops fanned into the border region after Iraqi government forces abandoned positions, leaving the Saudi and Syrian frontiers unprotected.

The satellite channel said it had obtained a video showing some 2,500 Iraqi soldiers in the desert area east of the Iraqi city of Karbala after pulling back from the border.

An officer in the video aired by al-Arabiya said that the soldiers had been ordered to quit their posts without justification.

The authenticity of the recording could not immediately be verified

Up to 45 people were killed in clashes between Iraqi security forces and followers of a radical cleric in the holy Shia city of Karbala signalling divisions among Shia factions as a Sunni insurgency rages.

The clashes erupted when police and army personnel tried to arrest Shia cleric Mahmoud al-Sarkhiaround midnight on Tuesday in the southern city of Karbala, an Interior Ministry intelligence officer and a police witness told Reuters.

Mr Sarkhi and his armed followers have clashed in the past with US forces, Iraqi security forces and supporters of Grand Ayatollah Ali al-Sistani, the most revered Shia cleric in Iraq.

Meanwhile, US authorities in Denver have arrested a woman accused of providing material support to the Islamic State of Iraq and Syria (ISIS) group, designated as a foreign terrorist organization, court documents showed.

According to a criminal complaint filed with the US District Court for the District of Colorado, Shannon Maureen Conley knew ISIS was engaged in militant activity and conspired to commit an offence against the United States.

It said she met a co-conspirator, only identified as YM in court papers, on the Internet sometime in 2013.

It said the pair "shared their view of Islam as requiring participation in violent jihad against any non-believers," and YM told her he was an active member of ISIS.

It said Ms Conley planned to travel to Syria via Turkey to meet YM, and first attended military tactics and firearms training with the US Army Explorers in Texas in February of this year.

The court papers said the aim of the training was for Conley to provide support and help to ISIS fighters. It said she and YM also planned for her to fight, if it was deemed necessary.