BAGHDAD (Reuters) - Civilians who managed to flee besieged Falluja have reported cases of starvation in the Iraqi city that government forces are trying to recapture from Islamic State militants, the Norwegian Refugee Council said on Thursday.

“If they stay in Falluja they face possible starvation, if they try to escape they risk being killed getting out,” NRC media coordinator Becky Bakr Abdulla said in a report, citing refugee accounts.

The Iraqi army launched an offensive on Monday to dislodge the ultra-hardline Sunni militants from Falluja, 50 km (32 miles) west of Baghdad. Falluja was the first Iraqi city to fall under IS control, in January 2014, and has been under a tight siege for about six months.

The NRC, which assists refugees at a camp south of Falluja, said the fighting made it difficult to assess the full extent of “the dire situation in the city”.

One woman told the NRC her family had lived on dry dates and drank from the Euphrates River before escaping Falluja.

About 50,000 are trapped in a city that now lacks drinking water, electricity and fuel, according to the NRC. About 40 families managed to flee in the past 36 hours, one of them saying they hid in a drainage pipe.

Aid agencies have become alarmed about civilian suffering and the United Nations has urged combatants to assure safe passage to inhabitants trying to escape the fighting.

The offensive to retake Falluja is part of Baghdad’s campaign to reverse IS’s capture of wide tracts of northern and western Iraq. Government forces retook the Anbar provincial capital Ramadi, near Falluja, in December.

Four civilians were killed and 19 wounded in artillery fire on Falluja’s center on Thursday, a source in the city’s main hospital said via the internet.

The death toll since the start of the military operation on Monday reached 47 - 30 civilians and 17 militants, he said.

The army has not yet reached the city and is battling the militants in surrounding villages, according to military statements that reported progress on several fronts, with the backing of a Sunni tribal force and Shi’ite militias.