The clash began when the law enforcers charged batons and lobbed tearshells and rubber bullets targeting the BNP men to disperse them from in front of the BNP Office in the city's Nayapaltan area around 1:00pm.
The agitated BNP supporters reportedly set fire to two police vehicles and also vandalized over 30 vehicles.
Additional Deputy Commissioner (Motijheel Division) of Dhaka Metropolitan Police Shiblee Noman said, at least 20 policemen also received injuries when the BNP activists hurled brick chips on them during the clash. They were undergoing treatment at Rajarbagh Police Lines Hospital.
Witnesses said that BNP standing committee member Mirza Abbas along with his several hundred supporters marched towards their party office around 12:30pm and staged a showdown there, halting traffic on the road.
Police tried to remove the BNP men to free the road. At one stage, police locked into an altercation with the BNP leaders and activists and started charging batons to disperse the activists, they said.
Thousands of BNP leaders and activists gathered in front of their office since morning as the party continued to sell its nomination forms for the third consecutive day on Wednesday among those who want to contest the 11th Parliamentary elections with its tickets, according to them.
Asked about yesterday's violence at Nayapaltan, Mirza Fakhrul said, "the attack  on leaders is affecting the election-time atmosphere. We condemn this."
He told reporters while replying to a query of journalists before entering Election Commission office.
Bangla Tribune quoting the BNP Secretary General said a group of helmet bahini youths covering their faces with black clothes set fire on police vehicles when the clash was going on between the law enforcers and the BNP activists in front of the party central office at Nayapaltan.
Earlier, he said, the same helmet bahini carried out attacks on the students, who were in a peaceful procession demanding safe roads across the country.
BNP Assistant Office Secretary Taipul Islam Tipu said that the clash ensued around 12:55pm as the police were trying to obstruct their leaders and activists from gathering in front of their office.
In a query, Anwar Hossain, Deputy Commissioner of Motijheel Division of Dhaka Metropolitan Police, said,  "BNP men hurled chunks of bricks at us and went on to torch two of our vehicles-and tried to set fire to more. We responded to in self-defenses,"
On 12 November, the party formally started the sale of nomination with the purchase of three nomination papers for its jailed chairperson Khaleda Zia.