UN leader Ban Ki-moon said Thursday he is worried by a guerrilla fightback in Mali and that no firm decision has been made to send a peacekeeping force there.
While praising France's month-old military intervention in the west African country, Ban said it would take weeks for the UN Security Council to decide the international community's next move.
"I think these military operations so far have been effective and successful. All these jihadis and armed groups and terrorist elements -- seemingly they have fled," Ban told a small group of reporters including AFP.
"Our concern is that they may come back. As you have seen yesterday they are hitting back in some areas."
Al Qaeda-linked Islamist rebels driven into remote mountains and deserts have switched to guerrilla tactics in territory they have lost to the Malian army and French forces. One landmine attack Wednesday killed four civilians.
"Our concern is that this may affect regional countries," Ban added.
"We don't know where they are hiding. They must be holed up themselves, hunkered down somewhere. Then, when the time comes, they may slowly come back. That is our concern."
Ban said the "effective, strong military operation" led by France will have "given them a big shock politically, psychologically, that the international community will never tolerate such terrorists."
France has called on the UN Security Council to start preparations to hand over to a UN peacekeeping force. But Ban indicated he was still cautious.
UN officials have highlighted that Mali's interim government has yet to accept a UN force.
"The (UN) secretariat has not made any decision," he told the reporters. "The situation is still fluid. We will have to see."
"We will continue to discuss and analyze the situation on the ground," Ban said, adding it would take "some weeks" for the Security Council to reach a decision on whether it was safe enough for a UN force to move in.
"It will take a few weeks because the French themselves are saying they still need to assess the situation on the ground to make that decision that it is time to transfer to some other body," he added.
Ban said he supported a decision by Mali's interim president Dioncounda Traore to call elections by July 31 as part of a roadmap to rebuild the government.
He said a UN political mission in Bamako would be increased to help the government. "I hope this election will take place with security ensured," he said.