It said 13 insurgents were killed — four of whom were wearing suicide vests — and five captured.
Afghanistan's Interior Ministry put the insurgent death toll in the attacks at 24, with five captured and no casualties on the police side.
The assaults on the sprawling Forward Operating Base Salerno in Khost province and nearby Camp Chapman came around 3 a.m., just as area residents were rising for early morning prayers.
The area, about 60 miles (100 kilometers) southeast of Kabul near the border with Pakistan, is a hotbed of activity by the Taleban and other insurgent groups, including the December attack on Chapman that killed four CIA officers and three contracted security guards.
Afghan police said about 50 insurgents attacked using rifles, heavy machine guns, rocket-propelled grenades and other weapons, but had been repelled.
After being driven away from the bases, the insurgents approached the nearby offices of the governor and provincial police headquarters but were driven off, said Khost provincial police Chief Abdul Hakim Ishaqzai.
"Given the size of the enemy's force, this could have been a major catastrophe for Khost. Luckily we prevented it," he said.
Small arms fire continued through the morning, while NATO helicopters patrolled overhead.
Police captured a pickup truck laden with ammunition along with a light truck packed with explosives that had become stuck in deep mud, according to Maj. Wazir Pacha of the provincial police headquarters. Bomb specialists later destroyed the truck and its cargo, according to the Interior Ministry.
NATO said the dead insurgents were members of the Haqqani Network, a group with deep ties to Al-Qaeda accused of launching frequent raids across the border from neighboring Pakistan.
An airstrike on a truck in which insurgents were fleeing killed Mudasir, a senior Haqqani explosives expert suspected of arranging suicide bomb attacks, along with two other militants, NATO said.
In the southern provinces of Nimroz and Zabul, a total of seven Taleban were killed in fighting, police said. No police casualties were reported.
Separately, NATO said one of its patrols mistakenly fired on a vehicle carrying private security contractors in Wardak province west of Kabul, killing two men.
It said the patrol had come under Taleban fire early Saturday, then spotted a vehicle approaching fast from behind with a man shooting out its window.
"It is believed that the private security contractors were returning fire against the same insurgents who had just previously attacked the coalition vehicle, and had increased their speed to break contact," the coalition said in a statement.
The incident was under investigation, it said.
Coalition forces and private security contractors frequently come under small arms fire along the stretch of road known as Highway 2 that runs west through perilous country toward the city of Herat.
On Friday, homemade bombs killed three US troops in southern and eastern Afghanistan, bringing the total number of foreign troops killed in Afghanistan this month to 55, including 35 Americans, according to a count by The Associated Press. July was the deadliest month for US forces in Afghanistan since the 2001 invasion, with 66 killed.
