Two Taliban suicide bombers killed at least 27 police and wounded around 40 in an attack on Thursday on buses carrying recently graduated cadets on the western outskirts of Kabul.
A police official said that, according to preliminary information, three buses were attacked as they approached the Afghan capital from neighbouring Wardak province.
"Initial information we have is that two suicide bombers were involved and there are many casualties," he said, declining to be identified by name.
An Interior Ministry official said at least 27 people were killed and 40 wounded.
The incident comes 10 days after an attack on a bus carrying Nepali security guards working for the Canadian embassy in Kabul that killed 14 people.
In April, at least 64 people were killed by a Taliban attack on a security services facility in Kabul in the deadliest bombing of its kind in Afghanistan since 2011.