"I condemn the attack on the #NATO convoy in #Kabul. The fight against terrorism continues. My thoughts are with all those affected," Stoltenberg wrote on Twitter.
According to media reports citing the Afghan Interior Ministry, at least eight civilians were killed by the explosion. The Islamic State terror group (outlawed in Russia) reportedly claimed responsibility for the attack.
The blast occurred amid the reported discussions in the United States to send additional troops to Afghanistan to help prop up the country's security forces. There are currently 8,400 US troops and 5,000 NATO troops in Afghanistan, and 3,000 additional troops are considered for deployment in the country, which saw more than 100,000 US troops at the height of the war, according to media reports.
Never miss a story again — sign up to our Telegram channel and we'll keep you up to speed!