Sayed Sadiq, a supporter of President Hamid Karzai and a strong opponent of drug trafficking, was the first lawmaker killed since the new parliament's inauguration.
Sadiq was a powerful local figure and a former commander of the Islamic Party run by Gulbuddin Hekmatyar, and twice worked as district governor.
Karzai said the death of Sadiq is a big loss for the people of Afghanistan. "He was a dynamic person and he devoted his entire life to brining peace and prosperity to the people of Takhar," he said.
In his last visit with the Afghan president, Sadiq said the central government was aware of which vehicles were being used to smuggle drugs and accused local officials of involvement in the trade.
Taliban activities have increased in Takhar recently. Afghan authorities have blamed the attack on Taliban.