Militants stormed at least two bases belonging to government forces in Badghis province overnight and ambushed a convoy of reinforcements. Officials said the group may have used the three-day truce, that ended Sunday, to plan the attacks.
"More than half of the fatalities came from the ambush and roadside bomb blasts that hit a reinforcement convoy," provincial governor Abdul Qhafoor Malikzai told AFP.
The other soldiers and police were killed when militants raided their bases, Qhafoor added.
The Taliban claimed responsibility for the attacks in a WhatsApp message to journalists.
Provincial council chief Abdul Aziz Bek confirmed the death toll and accused the Taliban of taking advantage of the suspension in fighting to do reconnaissance in the area.
"During the ceasefire the Taliban had sent informants to collect information about the bases and plan the attack," he told AFP.
Badghis governor spokesman Jamshid Shahabi told AFP that 15 Taliban fighters were also killed and 21 wounded in the attacks on two bases in Bala Murghab district.
The defence ministry issued a statement saying fighting in the area continued as the Taliban faced "stiff resistance" from Afghan security forces.
Further reinforcements had been deployed, the statement said.
It appeared to be the deadliest fighting since the Taliban returned to the battlefield on Monday after refusing a government request to extend their unprecedented three-day ceasefire.
Year-long truce offer
President Ashraf Ghani announced over the weekend that the government's eight-day ceasefire, which had been scheduled to expire on Tuesday, would be prolonged for another 10 days.
The first formal nationwide ceasefire since the 2001 US-led invasion had sparked extraordinary scenes of Taliban fighters, security forces and civilians happily celebrating the Eid al-Fitr holiday together.
But the jubilation appeared to alarm Taliban leaders, who on Sunday ordered their fighters to stay at their posts or in areas under their control.
The Taliban hailed the truce as a success and a demonstration of their "full control" over their fighters.
The government's move to extend its ceasefire with the Taliban may buy Ghani more time to work out how to keep the momentum going.
His February offer of peace talks with the Taliban, considered to be one of the most comprehensive plans ever offered by an Afghan government, was ignored by the militants, who went on to launch their annual spring offensive.
The insurgents have repeatedly demanded direct dialogue with the United States, which Washington has refused, and the withdrawal of foreign troops.
Ghani said Tuesday he was prepared to extend the ceasefire to a year "if the Taliban accepts it", according to a video of a meeting between the president and a group of peace marchers who arrived in the capital on Monday.
The government's ceasefire does not extend to the Islamic State group, which claimed responsibility for two suicide attacks in the eastern province of Nangarhar over the weekend that marred an otherwise peaceful Eid holiday.
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