The explosion occurred in the province's Gereshk district around 8 p.m. (15.30 GMT) on Friday and was so severe and strong that a security post near the bridge in Gereshk Bazar on Herat-Kandahar Highway and a police checkpoint were completely destroyed, with all soldiers there killed, according to the information provided by a security source.
The Taliban movement has taken responsibility for the attack, claiming that it had killed 16 Afghan soldiers.
In pursuit of its recognition, the Taliban have been leading the insurgency against the Afghani government since the early 2000s, while also demanding all foreign troops to withdraw from the country.
The group has been accused of providing terrorist organisations such as al-Qaeda* (banned in Russia) and Daesh* with safe haven in Afghanistan.
*Daesh (also known as ISIS/ISIL/IS) and al-Qaeda are terrorist groups outlawed in Russia