Afghan security forces are fighting the Taliban in the southern city of Kandahar, a day after the insurgents raided the city's sprawling airport, killing at least 18 people and taking six people hostage.
There was some uncertainty over the exact casualty figures with security forces hunting as many as five insurgents who had survived hours of fighting.
"The operation is going very slowly as the Taliban have taken six people hostage including two women and two children, so we have to act cautiously," said Dawood Shah Wafadar, commander of the 205 Atal army corps in southern Afghanistan.
He said at least 18 members of the security forces and civilians had been killed and 11 wounded, including two women.
Nine Taliban had been killed out of a 14-strong assault force.
The Taliban said in a statement 150 soldiers had been killed but the movement has often made exaggerated casualty claims in the past.
A spokesman for NATO's Resolute Support mission said there had been no reports of casualties among the hundreds of international personnel at the air base but he had no other details.
The raid in one of the Taliban's traditional strongholds risked overshadowing the Heart of Asia security conference in Islamabad, where President Ashraf Ghani made a plea for more regional support to end the insurgency.
The Taliban, fighting to re-establish hard-line Islamist rule after US-led military intervention toppled their regime in 2001, have been struggling to settle a leadership dispute which has seen scores killed in fighting between opposing factions.
But the attack on one of the most heavily protected air bases in the country underlined their ability to inflict serious damage on security forces still shaken by the Taliban's brief capture of the northern city of Kunduz in September.
Officials said the fighters had attacked a perimeter area of the huge and heavily fortified complex on Tuesday evening (local time), initially taking up position in a school in a residential area.
The site in Kandahar, Afghanistan's second biggest city, contains both a civilian airport and a large military base that houses thousands of NATO military personnel and civilian contractors in addition to Afghan forces.
The Taliban statement said suicide attackers armed with both light and heavy weapons had entered the base and attacked international forces and their Afghan allies.