QUETTA, Pakistan — A powerful roadside bomb exploded near a vehicle carrying Pakistani security forces, killing two soldiers in the southwestern city of Quetta, the capital of the restive Baluchistan province, a police official said Tuesday.

Sixteen Taliban militants were killed and six others wounded in five provinces since early Tuesday, the country’s defense ministry confirmed on Wednesday.

More than 100 militants have surrendered to Afghan government forces over the past two days amid increasing military pressure on the Taliban, officials said Tuesday.

The escalation between the United States and Iran over the killing of an Iranian commander now has sparked deep concerns about prospects for the peace process in Afghanistan, with officials and experts warning that Iran could collaborate with the Taliban to thwart American efforts in the war-torn country.