Police and paramilitary troops in diverted traffic and frisked pedestrians in the Bangladesh capital, Dhaka, yesterday after the opposition Awami League threatened to besiege a private office of Prime Minister Begum Khaleda Zia.

The Awami League has asked Khaleda ? who is only half way through a five-year elected term ? to resign by April 30 and to test her popularity in an early election. She has refused and has vowed to punish anyone trying to stir anarchy.

Authorities tightened security on the streets and avenues around Khaleda?s office at ?Hawa Bhaban?, from which she often runs the activities of her Bangladesh Nationalist Party (BNP).

?We are keeping an eye on people coming to the city at a sensitive time and are picking up those who cannot explain the reason for travelling,? one police officer said.

Police have arrested 2,500 people in the past two days in a crackdown to deter people from entering the capital to carry out subversive acts.

An election is not due before October 2006, but the Awami League, headed by former prime minister Sheikh Hasina, wants early polls.

?We will proceed with the siege plan as this is part of our campaign to force Khaleda Zia out,? said Hasina?s political secretary, Saber Hossain Chowdhury.

However, the siege would be peaceful unless the party was provoked, he said.

Escalating tension prompted many shops and schools on roads near Khaleda?s party office to close, witnesses said.

Awami leaders said party members had begun to gather and would start the push towards Hawa Bhaban any time.

Opponents accuse Khaleda?s government of being corrupt, inefficient and repressive, charges she has denied.