Two gunmen, who were riding a motorcycle, shot at Fakhrul Islam outside his home in Halanaka area of Hyderabad city this afternoon. Islam was hit by several bullets and died instantly, police officials said.
The gunmen escaped after the attack. No group claimed responsibility for the killing.
Islam had filed nomination papers to contest polls to both the Sindh Assembly and the National Assembly or lower house of parliament.
Pakistan will go to the polls on May 11, marking the first democratic transition of power in the country's history.