Police in Bangladesh fired teargas and used batons on Wednesday to disperse opposition activists preparing to besiege a party office of Prime Minister Begum Khaleda Zia.
Police fired at least 12 rounds of teargas shells, injuring about 10 people. They also detained dozens of activists of the main opposition Awami League party, including women, witnesses said.
"We have orders from the home ministry not to show any indulgence to troublemakers," said a police officer who declined to be identified.
"We will do everything necessary not to let law and order lapse further."
Police intercepted the opposition activists in the areas of Gulistan, Paltan, Motijheel and Shahid Minar in the capital in the afternoon.
The Awami League, headed by former prime minister Sheikh Hasina, has asked Khaleda - who is only halfway through a five-year elected term - to resign by April 30 and to test her popularity in an early election.
Khaleda has refused and has vowed to punish anyone trying to stir up protests.
Authorities tightened security on the streets and avenues around Khaleda's office at "Hawa Bhaban", in the city's Banani area, from which she often runs the activities of her Bangladesh Nationalist Party (BNP).
Witnesses said police virtually besieged the central office of the Awami League at Gulistan and also guarded strategic points in the city in a bid to keep opposition activists off the streets.
Escalating tension prompted many shops and schools on roads near Khaleda's party office to close, witnesses said.
Opponents accuse Khaleda's government of being corrupt, inefficient and repressive, charges she has denied.