"They were clearly armed and they were clearly hostile and that is why they were engaged"
Major John Thomas, Isaf spokesman
An earlier raid on Friday in which a number of civilians were killed is understood to have angered Karzai.
The International Security Assistance Force (Isaf) said the deaths on Friday night came after fighters were seen preparing to attack a base in Paktika province.
Major John Thomas, Isaf spokesman, said: "They were clearly armed and they were clearly hostile and that is why they were engaged."
Isaf forces conducted reconnaissance to confirm their suspicions and the suspected Taliban fired on a US-led multinational-force aircraft, he said.
Major Donald Korpi, an Isaf spokesman for eastern Afghanistan, said "up to 60 Taliban were killed".
Thomas did not give a figure for the dead but did not dispute the toll, saying that such numbers were arrived at through various battle damage assessments.
Commanders in the area said it was the largest formation of Taliban fighters there since January, he said.
The US-led multinational force reported separately that soldiers working with Afghan troops had killed nearly 20 "enemy fighters" in a seven-hour battle in the southern province of Kandahar, the birthplace of the Taliban movement.
About 1,500 Taliban suspects since March,
the interior ministry says [AFP]
The attackers had initiated the battle by opening fire with machineguns, it said in a statement.
Several more fighters were reportedly killed in the adjoining province of Uruzgan when a firefight erupted after troops were shot at with multiple rockets.
The Afghan interior ministry announced on Saturday that Afghan and foreign security forces had killed more than 1,500 suspected Taliban fighters in about 80 operations across the country since March.
About 530 more, including 23 would-be suicide bombers, had been captured, the ministry said in a statement.
Mine clearers held
Also on Saturday, suspected Taliban fighters abducted 17 Afghan mine clearers in southern Afghanistan, police and their organisation said.
The 17 were kidnapped while travelling in Ghazni province, Mohammad Shohab Hakimi, the head of the Mine Detection and Dogs Centre, said.
Hakimi said men identifying themselves as Taliban fighters had called his organisation to say they were holding the men.
He said: "Taliban called us and told us that they were abducted with all their materials. They have some questions for them and after that they're going to be released."