Thousands of Awami League supporters marched through Dhaka demanding President Iajuddin Ahmed step down as head of the interim administration, the BBC reported.
The multi-party alliance, led by former Prime Minister Sheikh Hasina, has charged fraud in the Jan. 23 election.
Charges included that the list of eligible voters was out of date and that some members of the election commission are biased toward Hasina rival former Prime Minister Khaleda Zia.
Demonstrators threatened to surround the president's palace.
The Awami League, or People's League, is said to have been the political catalyst for Bengali discontent and rebellion in 1971.