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The assault on the headquarters in Gardez, which was still continuing, was launched at 6:00 AM, said the regional police commander, Asadullah Shirzad.
Five civilians were among the wounded.
One of the five attackers was still holding out more than five hours after the coordinated assault began, Shirzad said.
"The first attacker blew up his vehicle at the entrance to the headquarters, opening the way for two others who opened fire on security forces, and another suicide bomber was shot dead," he said.
The head of the police hospital, Dr Shir Mohammad, confirmed the casualty toll.
Taliban spokesman Zabihullah Mujahid claimed responsibility for the attack in a statement.
Since the beginning of their spring offensive in late April, the Taliban have been mounting lethal attacks on the positions of the Afghan army and police, who have lost several dozen men in recent weeks.
Foreign forces assisting the Afghans have also been targeted. Seven US soldiers were wounded yesterday in an insider attack at a military base by an Afghan soldier described as a "patriot" by the Taliban.
They are battling to topple the government of President Ashraf Ghani and oust the Western forces that support him.