Taliban bombers have attacked an Afghan police convoy outside the capital Kabul, killing at least 30 people and wounding 50 others, officials say.
Two bombs hit a convoy of buses carrying graduates from a ceremony on the city's western outskirts.
Paghman District Governor Musa Khan told the BBC that all but two of the dead were police cadets.
The bombing was claimed by the Taliban and followsan attack on a bus just over a week ago that killed 14 people.
A Taliban spokesman said that in Thursday's attack, the first bomber attacked one bus and when rescuers began to arrive the second drove an explosives-laden car into their vehicles.
The cadets were returning to Kabul from a training centre in Wardak province and were about to go on leave.
The Taliban's main targets are the Afghan government, international organisations and foreign military, but in particular the Afghan army and police force.
There have been numerous attacks on the Afghan police, even when the officers are unarmed. They are perhaps a softer target than the army, using un-armoured vehicles and lighter weapons.
The Taliban have tried to increase their attacks recently, especially after the appointment of their new leader.
Big attacks make headlines, but there have been many foiled attacks that are not widely publicised.
Taliban violence normally increases at this time of year, but this year there is an unusual upsurge in several provinces.
On top of that, the authorities have also for the first time engaged in several stand-offs with the Islamic State group in the east, which has forced hundreds of families to flee their homes.