A suicide bomb attack has killed at least 20 people and injured about 30 in the south-west Afghan city of Zaranj, according to officials.
A district police chief and a border reserve police commander were among the dead, said Ghulam Dastgir Azad, governor of Nimroz province.
The device went off outside a mosque in a popular market and there may have been two bombers, he added.
At least 12 militants were killed elsewhere, Afghan officials say.
Men were getting ready for evening prayer on Thursday at the mosque when the bomb exploded.
Mr Azad feared the death toll might rise as some of the injured were in a critical condition.
There was no immediate indication of who was responsible, but similar attacks have been blamed on Taleban militants.
The 12 militants were killed in the province of Ghazni in two separate clashes, Afghan officials said.
The country is witnessing a surge in violence, with the Taleban fighting the government of President Hamid Karzai and the tens of thousands of foreign troops deployed there.
Zaranj is the capital of the Nimroz province, which borders Iran.
It is one of the few Afghan provinces which does not have a permanent presence of international troops and it has seen an increase in violence over the past few months, the BBC's Alastair Leithead reports from Kabul.
It is thought the Taleban influence has been growing as fighters have moved across the border in Helmand, where they have increasingly been coming under pressure from international forces, he says.
An early estimate from the United Nations suggests the growth of opium poppies is expected to increase this year in Nimroz.