She has been there since Saturday night after police presence was bolstered around the office.
Police locked the BNP headquarters as well on the same night.
TV footage showed the former prime minister sitting in her white SUV.
Police locked all her office gates on Monday.
Khaleda on Sunday told the BBC Bangla that she was being confined but Prime Minister Sheikh Hasina said the BNP chief was free to get out anytime she wanted.
BNP leaders were seen pushing and kicking the locked gates in a bid to break free.
A woman leader even tried to climb it.
Police responded with what seemed like pepper spray.
Several women leaders of the party including Syeda Asifa Ashrafi Papiya, Selima Rahman, Shirina Sultana, Nilufa Chowdhury Moni were leading the protests from behind the locked gate.
Earlier, the party's acting Secretary General Mirza Fakhrul Islam Alamgir called on BNP supporters to "kick and break the locks".
BNP leaders inside Khaleda's office were waving flags and shouting anti-government slogans.
But it is unclear when the former prime minister will be finally able to get out.