US President Barack Obama has requested $8.8 billion to fund the fight against the Islamic State group in his 2016 budget unveiled Monday.

A total of $5.3 billion would go to the Pentagon to finance Operation Inherent Resolve, which was launched in August with a series of airstrikes against militants in Iraq and Syria.

Last week, defense officials told AFP that US and coalition aircraft had carried out 705 bombing raids around the Syrian town of Kobane since September 23 after it was captured by jihadists.

The State Department, which has been leading efforts to build a multinational coalition against the IS group, has requested a further $3.5 billion.

The money would "strengthen regional partners... provide humanitarian assistance and strengthen Syria's moderate opposition," Deputy Secretary of State for Management Heather Higginbottom said.

The funds would also boost "collaboration with coalition partners to degrade and ultimately destroy ISIL," she added, using another acronym for the group.

"ISIL poses an immediate threat to Iraq, Syria, and American allies and partners throughout the region as it seeks to overthrow governments, control territory, terrorize local populations, and attack the United States and coalition partners throughout the world," Obama's budget request says.

"The on-going conflict in Syria also continues to threaten regional stability and has displaced over 10 million people," it adds.

"The budget provides funding for military operations, diplomacy, governance, and humanitarian and security assistance programs to address these challenges."

Higginbottom said a further $1.1 billion had been requested by the State Department to fund diplomatic efforts in Iraq, where IS is holding a large swath of territory.