Unidentified attackers threw a hand grenade at a police van in Pakistan's northwestern city of Peshawar, killing a police officer and wounding two other officers and a bystander before fleeing the scene, police said. No one immediately claimed the attack.
Police say they have launched an investigation into the attack on July 30 at the Karkhano Market.
In a statement, Peshawar police said the attack happened while officers were visiting the market to ensure people were adhering to social distancing rules to curb the spread of the coronavirus.
Pakistani authorities have tasked police and government administrators of ensuring that people wear face masks and take other precautions after the country saw a spike in COVID-19 cases flooding hospitals last week.
The Karkhano Market is known for its smuggled imported goods with large crowds visiting daily from all over Pakistan.
Peshawar is the capital of Khyber Pakhtunkhwa Province, which borders Afghanistan. The Pakistani military has carried out several operations against militants in Khyber Pakhtunkhwa.