People started gathering at Jantar Mantar here at around 10 AM and sat in silence.
Aam Aadmi Party leaders Arvind Kejriwal, Manish Sisodia and Kumar Vishwas also joined the protest along with some of their supporters with their mouth tied with black cloth.
Aam Aadmi Party National Convenor Arvind Kejriwal tweeted, "her death is a matter of shame and sorrow for all of us. Let's resolve that we will not let her death go in vain.
"Aren't we all responsible for her death? Can we all now do something so that half of humanity starts feeling safe amongst us?" he said.
The mourners protested against the security lock down of India Gate and Raisina Hill where violent demonstrations were witnessed last weekend over the rape.
"The government is not even allowing mourning of the death. This is insensitivity. There is complete lock down. You have the metro stations shut. You have a road completely blocked. This is undemocratic," a protester Sunil said.
Sisodia said the government was muzzling the voice of people by shutting Metro and closing down India Gate.
In a statement, AAP said the girl, who became the symbol of womens insecurity and their courage, is no more.
"This is a moment of national grief. This is also a moment of national shame. We, as a nation, have failed to provide conditions in which women can lead a normal life without being subjected to indignities. We, as a society, have failed to evolve a culture of respect and equality for women.
"This event and the subsequent developments have no doubt generated widespread outrage and justified anger. But today we must convert this into a positive resolve. Let us all resolve that we shall convert this moment into a movement to end all forms of violence against women. Let No Violence Against Women be our national new year's resolution," it said.
In tweets, activist Kiran Bedi said, "today is a day of reflection and personal audit on the way we as parents and teachers are grooming boys in this country.
"Today is day of mourning on lives we have lost because of failure of our criminal justice system and resolve to not fail it in future. Today is a day to also reflect the way we project our women in media," she said.