Police tightened security around the Bangladesh Election Commission headquarters in the capital on Thursday as thousands of activists laid siege to the building to press for the dismissal of the poll body.
A 14-party alliance led by Sheikh Hasina wants Chief Election Commissioner MA Aziz and his deputies to quit ahead of polls due in January and have threatened increased civic action unless they go.
Hasina, a former prime minister and more recently the main opposition leader, accuses the commissioners of bias towards the Bangladesh Nationalist Party (BNP), which stood down after five years rule last month ahead of January's polls.
The BNP is led by Begum Khaleda Zia, the immediate past prime minister and an arch-rival of Hasina, who heads the Awami League.
Riot police took position around the commission building as activists blocked nearby roads, halting traffic for hours.
"Aziz and his cronies are biased and unable to hold a free election. They must go," Jahangir Kabir Nanak, a leader of Awami League's youth front, told protesters.
He said Aziz was working "according to a BNP blueprint to ensure Khaleda regains power through election fraud".
A group BNP leaders met Aziz at his office on Wednesday and asked him not to give in to pressure.
Aziz has insisted he will not step down even if asked to by the country's interim government, which is to supervise the election.
The interim government is headed by state president Iajuddin Ahmed and Hasina has given him until Sunday to prove his neutrality or face increased protests.
At least 30 people have died in political violence since Khaleda was constitutionally obligated to resign last month.