Swat district police officer Zahidullah Khan said the diplomats were visiting the Swat valley area on the invitation of local chamber of commerce.
"The squad that was leading the convoy was hit by a roadside bomb," he said.
Another four police officers were wounded, Khan said.
All the nearly dozen diplomats were safe and were heading back to Islamabad, police said.
"All the ambassadors remained safe in the attack and had been shifted to a safe place before their departure to Islamabad," Deputy Inspector General of police Mohammad Ali Gandapur told Reuters.
The nationality of the diplomats was not immediately clear. A Pakistani foreign office spokesperson did not immediately respond to a request for a comment.
No one claimed responsibility for the attack.
Pakistani counter-terrorist forces maintain a strong presence in the Swat valley, which has long been a hotbed of Islamist militant insurgency. The militants have stepped up their attacks since late 2022 after breaking a ceasefire with the government.
In 2012, Islamist militants shot and wounded Nobel Peace Prize laureate Malala Yousafzai in the valley.
7°C