A new U.N. report says security threats from violent extremists and criminal groups in Mali are "alarming" and the government must deploy more troops to the volatile north and step up efforts to reform its military and police.

Secretary-General Ban Ki-moon says in the report to the Security Council that in spite of improved relations among signatories to last June's peace agreement, north and central Mali remain threatened by "criminal, violent extremist and terrorist groups, which take advantage of the limited presence of Malian law enforcement institutions."

Mali's northern half fell to Islamic extremists following a military coup in 2012. A French-led military intervention drove them out of major towns, but the region remains insecure. Over the past year, jihadis have mounted a growing wave of violent attacks.