U.N. experts say the political and security vacuum in Libya has been exacerbated by the Islamic State group which has significantly expanded its control over territory in the conflict-torn country.

The experts said in a report to the U.N. Security Council circulated Thursday that all parties in the conflict are continuing to receive illicit arms transfers, some with support from member countries.

These weapons are not only influencing the instability but are having "a negative impact on the security situation in Libya and its political transition," the report said.

Libya has effectively been a failed state since the 2011 ouster and death of longtime dictator Moammar Gadhafi which led to the country's military collapse and fragmentation by powerful militias.