Nigeria has limited the reach of Boko Haram extremists even though the group can still launch attacks, the country's information minister has said.
Boko Haram used to administer a number of local governments and collect taxes but now has none under its control, the minister, Lai Mohammed, added.
The extremists used to be active in 10 states but are now confined to a much smaller space, he said.
"They've been completely degraded," he said on Tuesday.
"They don't have the capacity to launch the kind of attacks they did before, but like with all asymmetrical wars, you cannot stop the suicide bombs or the attacks on soft targets.
"But clearly the government is winning.
"It's a war that can be won."
President Muhammadu Buhari's recovery from a health problem is on track despite a stopover in London on his way back to Nigeria after attending the United Nations General Assembly in New York, he said.
Mr Buhari's London stop had raised concerns because the 74-year-old president has twice this year spent several weeks in London for treatment of an undisclosed illness.
The president has sought treatment in Britain rather than in Nigeria because of the type of treatment available in London, Mr Mohammed said.
"We don't have the facilities or the expertise that's needed for his illness," the minister said, declining to provide specifics.
"I think Mr President should be left to decide whether he wants to disclose his ailment or not," Mr Mohammed said.
"I don't think he should be under any obligation to do so."