The bloodshed began on Friday with a truck bomb that exploded in a heavily populated district of the capital and ended with an hours-long battle at a base used by U.S. special forces. It became the deadliest day in Kabul for years.
The Islamist insurgents claimed responsibility for both the police academy attack and the battle at the U.S. special forces base, though not for the truck bomb.
The violence was a stark reminder of the difficulty of reviving a stalled peace process, conveying a no-compromise message from the Taliban following last week's revelation of Mullah Mohammad Omar's death and a dispute over the leadership of the insurgency.
"The question is, who is sending the message?" said Thomas Ruttig of the Afghanistan Analysts Network.
The U.N. mission in Afghanistan said the incident was the worst since it began recording civilian casualties in 2009, with 355 civilians killed or injured. The U.N. Special Representative, Nicholas Haysom, called it "extreme, irreversible and unjustifiable in any terms".
On Saturday, NATO-led coalition forces confirmed that one international service member and eight Afghan contractors had been killed in the attack on Camp Integrity, a base used by U.S. special forces near the main airport.
The blast outside the base was powerful enough to flatten offices inside, wounding occupants who were airlifted by helicopter to military hospitals during the night.
"There was a big explosion at the gate ... (The gunfire) sounded like it came from two different sides," said a special forces member who was wounded when his office collapsed.
View galleryDeadly suicide attacks in Kabul
Afghan security personnel inspect the site of a car bomb attack in Kabul, Afghanistan, Friday, Aug. …
The initial blast caused by a suicide car bomb at the gate was followed by other explosions and a firefight that lasted a couple of hours, he said.
Camp Integrity is run by U.S. security contractor Academi, which was known as Blackwater before being sold to investors. Academi did not immediately respond to requests for comment.
"The helicopters went on for hours... medevac-ing people out," a U.S. contractor at a camp nearby said.
In Washington, the White House said National Security Advisor Susan Rice had spoken with Afghan President Ashraf Ghani by telephone to express U.S. condolences.
President Barack Obama's counterterrorism adviser, Lisa Monaco, also spoke with Afghan National Security Advisor Hanif Atmar.
"Ambassador Rice and Ms. Monaco each reaffirmed U.S. support for Afghanistan as it confronts terrorists who target innocent civilians and threaten the stability and security of Afghanistan," the White House said in its statement.
The Camp Integrity assault followed a suicide bombing at a police academy on Friday evening that killed and wounded more than 40 people, the Afghan Interior Ministry said. A police source said the final tally was higher - 26 killed and 28 wounded.
"The bomber was wearing a police uniform and detonated his explosives among students who had just returned from a break," a police official said.
Taliban spokesman Zabihullah Mujahid said the insurgents had launched both the police academy and Camp Integrity attacks, but refused to comment on Friday's early-morning truck bomb, which tore through buildings in central Kabul, killing at least 15 people and wounding 248 others.
The Taliban, who were toppled from power by the U.S.-led military intervention in 2001, rarely admit to attacks that kill a high number of civilians.
Divisions have broken out within the Taliban high command following last week's appointment of Mullah Akhtar Mansour as leader. Previously seen as open to reviving peace talks, he has since pledged to press on with the insurgency, which has killed or wounded thousands this year.
The conflict between the Western-backed government and the Taliban has intensified since the NATO combat mission ended last year, but Afghan security forces and civilians have borne the brunt of the violence.
Analyst Ruttig said that, with the latest attacks in Kabul, Mansour could be sending a message of resolve to the militant rank and file as well as to the Afghan government.
On the other hand, Taliban factions opposing Mansour's leadership could be seeking to kill off any hope of future talks by launching their own wave of violence.
"The hope of some people was that the death of Mullah Omar would put the Taliban in disarray and possibly weaken them," Ruttig said. "I think that was a little over-optimistic."
The death at Camp Integrity was the second of an international service member in Afghanistan this year. The victim's nationality was not released.
Almost 5,000 civilians were killed or wounded in Afghanistan in the first half of the year, according to U.N. figures.