NEW DELHI — Having trumped a government effort to defuse his anticorruption movement, the protest leader Anna Hazare announced that he would leave a city jail on Friday and begin a mass demonstration and hunger strike at a public ground in the national capital.

Mr. Hazare had initially suggested that he would emerge from Tihar Jail on Thursday and lead a public protest against corruption at Ramlila Maidan, a large outdoor public space in New Delhi. But with an enormous crowd expected to participate, Mr. Hazare’s aides announced on Thursday that another day was needed to adequately prepare the protest site.

“I just spoke to Anna ji, in view of conditions of Ramlila Maidan,” an aide, Arvind Kejriwal, said in a news release, affixing the Hindi-language honorific of “ji” to Mr. Hazare’s name. “Anna ji will reach Ramlila Maidan tomorrow.”

The delay means that for another night Mr. Hazare will remain inside Tihar Jail, where he has been fasting since his controversial arrest on Tuesday. Thousands of people have poured into the streets in different Indian cities this week to express support for Mr. Hazare and his campaign to create a new, independent anticorruption agency with sweeping powers to investigate government officials.