At least one person died Wednesday and scores were injured in the Bangladeshi capital Dhaka as police fired rubber bullets and tear gas at thousands of opposition supporters, police and witnesses said.

Tension has been building this week after the main opposition Bangladesh Nationalist Party (BNP) called a massive rally for Saturday in an effort to force Prime Minister Sheikh Hasina to resign.

Opposition spokesman Shahiduddin Chowdhury Annie said police fired at around 5,000 opposition supporters who peacefully gathered outside the BNP main office in central Dhaka on Wednesday.

"We allowed traffic to move. But police suddenly attacked us, firing at our activists and supporters. At least 100 people were injured," Annie said.

The BNP said at least two of their activists, including a student leader, were killed by police fire.

Live Facebook footage shared by the BNP -- which could not be independently verified -- showed apparently injured party activists lying on the stairs of the office.

Abdul Hye, a police constable posted at Dhaka Medical College Hospital, told AFP that the dead body of one person and at least eight injured people were brought to the hospital.

He could not say whether the body was hit by live or rubber bullets.

Dhaka Metropolitan Police spokesman Faruq Ahmed blamed the BNP for the clashes, saying they were trying to clear roads for traffic when party activists attacked law enforcement officers with rocks and molotov cocktails.

"We fired rubber bullets and tear gas to evacuate the people from the road," he said, adding that thousands of BNP activists were at the scene at the time of the clashes.

The clashes came after BNP officials expressed fears that the police would trigger violence to scuttle Saturday's rally, which the party expects will draw hundreds of thousands of people.

Rizvi Ahmed, another party spokesman, said at least 1,430 BNP activists and supporters had been arrested since November 30 in an attempt to stop the rally taking place.

The BNP want Hasina to resign and for a caretaker administration to govern until fresh elections are held.

The BNP was decimated in the past two general elections, which independent observers said were heavily rigged by Hasina's government.

Fifteen Western embassies issued a joint statement ahead of the rally late Tuesday, calling for the country to allow free expression, peaceful assembly and elections.