At least 18 people have been killed and dozens injured during sporadic fighting in the Iraqi city of Samarra after armed men took control of several districts, military sources have said.
Government forces in the city told Al Jazeera that they believed the men were members of t he Islamic State of Iraq and the Levant group (ISIL) and that the army was sending in reinforcements to face them.
They said the fighting was ongoing and that government warplanes were attacking rebel positions in the city, which lies 125 km north of the capital Baghdad.
Sources said the men entered the city in large numbers from the south with heavy weapons attached to pick-up trucks.
ISIL, which grew from the remnants of a now disbanded al-Qaeda-allied group, has been strengthened by involvement in the war in neighbouring Syria and now holds parts of the city of Fallujah, just 65km from Baghdad.
On Thursday, the International Committee of the Red Cross said it had delivered medical supplies to Fallujah for the fst time since January, describing conditions in the city as "extremely dire".
"The situation is very worrying," said Patricia Guiote, head of the Red Cross sub-delegation in Baghdad and the leader of the five-member team that delivered the supplies to Fallujah.
"People are enduring a severe shortage of food, water and health care. Services at the hospital, which is the only facility still able to provide treatment for the injured and the sick, have been seriously affected by the fighting."
The ICRC said the team delivering the supplies found "immense needs and a situation that is extremely dire."
"People in the city are living through a terrible ordeal."
Rise in bloodshed
Upwards of 350 people, most of them civilians, have been killed in months of conflict in Fallujah, according to Doctor Ahmed Shami at the city's hospital.
Violence in Iraq is running at its highest levels since 2006-2007, the height of the country's Sunni-Shia sectarian conflict.
More than 900 people were killed last month, according to figures separately compiled by the United Nations and the government. Over 4,000 have been killed so far this year, according to AFP news agency figures based on security and medical sources.
Officials blame external factors for the rise in bloodshed, particularly the civil war in neighbouring Syria, and insist wide-ranging operations against ISIL and other groups are having an impact.
But the violence continues unabated, with analysts and diplomats saying the Shia-led government needs to do more to reach out to the disaffected Sunni minority to reduce support for rebels.