Some 300 people protested for a second day in the Afghan city of Herat against Iran's weeklong blockage of fuel tankers seeking to enter Afghanistan.
The protesters marched to the Iranian consulate carrying banners with slogans including "Death to Iran."
In Kabul, Afghan Commerce Minister Anwar ul-Haq Ahadi said nearly 2,000 fuel trunks were waiting at a border crossing some 100 kilometers away from Herat, and that only 40 were allowed to leave Iran each day.
"The stopping of our tankers on the Iranian border has caused big damage to our private sector. We are in continued negotiations with Iran. Their reasons are not convincing us and are not justified reasons," Ahadi said.
Ahadi said Kabul had asked Kazakhstan to sell Afghanistan some 200,000 tons of fuel immediately.
Iran says the slowdown is due to "technical problems" related to the reduction of Iranian fuel subsidies.