U.N. Secretary-General Antonio Guterres says Somalia is making progress toward building a functioning state but must tackle violent extremism, terrorism, armed conflict, political instability and corruption.

He says in a report to the U.N. Security Council circulated Monday that these challenges "demonstrate the fragility of the gains made so far" and "threaten progress."

After three decades of civil war, extremist attacks and famine, Somalia established a functioning transitional government in 2012 and has since been working to rebuild stability.

But Guterres said "the security situation remained volatile" between mid-December and early May. He said the al-Qaida affiliated Al-Shabab extremist group continues to be "the main perpetrator of attacks against government facilities, government officials and security forces as well as popular restaurants and hotels."