Four doctors working at a prison in the Afghan capital Kabul were among five people killed by a bomb attached to their car, police say.
Three of the dead were women. The fifth was their male colleague's driver.
The doctors were travelling to Pul-e-charki prison where they worked when the "magnetic" bomb detonated. No group has said it carried out the bombing.
Dozens of militant attacks in Kabul have left more than 100 people dead in the past two months.
Journalists, activists and other political figures have been targeted. Several recent attacks on individuals have used "sticky bombs", attached to vehicles by magnets.
Levels of violence in the country have remained high despite the start of negotiations between Afghan and Taliban officials.
Police said two other people were wounded in Tuesday's early morning blast in the south of the capital, where Pul-e-charki is located.
Among the jail's inmates are hundreds of Taliban militants, featured in a BBC report last year.