Bangladesh's opposition leader is accusing Sheikh Hasina Wajed, the prime minister, of trying to cling to power by force, as police clamp down on protests on the first anniversary of disputed elections.

Riot police have confined Khaleda Zia, leader of the main opposition Bangladesh Nationalist Party (BNP), to her office since Saturday to stop her from leading rallies in protest against alleged vote-rigging a year ago.

On Monday, authorities stepped up their siege of Zia's office in Dhaka by parking 11 lorries laden with sand and bricks outside the office compound. They then padlocked the gates.

At least four people were killed and dozens injured in Monday's clashes between followers of the BNP, police and Hasina's ruling Awami League.

"Not only am I prisoner, but the whole of the country is being held captive. What kind of country are we living in?" Zia said.

Zia labelled the government 'illegal' on Monday while Hasina blamed her for the attacks reported across the country [EPA]

Hasina responded by saying that Zia was trying to create anarchy and blaming Zia for the attacks reported across the country.

"I am urging the BNP leader to stop these bomb and grenade attacks, these acts of sabotage, and killings, of arson and damage to property," Hasina said in a speech to the nation, exactly a year after she was re-elected in polls boycotted by the BNP.

When dozens of Zia's supporters tried to break the siege, riot police fired pepper spray at them.

Television footage showed BNP members wiping away tears after they tried to prise open the gates of the compound in Dhaka's Ghulshan district.

Zia's spokesperson earlier said she would attend a mass rally and called on her supporters to attend as well.

She could be seen sitting in her car, with the engine revving. She later spoke to journalists who managed to sneak over the wall.

"This government is illegal because it was not elected by the people. They sprayed pepper at us. It is not a normal situation. Is the country facing a war?" Zia said, calling the government "illegal" and urging people to join protests.

"They want to hang on to power people by bullets, tear gas and bombs.

"The protests will continue ... No dictator can cling to power like this."

Source: Agencies