An Indian court ordered the release of three leaders of the youth-led "Cockroach" movement on Sunday, a day after a sweeping police crackdown in New Delhi.

Founder Abhijeet Dipke and fellow leaders Saurav Das and Ashutosh Ranka were detained when they landed in Delhi on Saturday. They had planned to lead a rally against a review of India's voter lists. The group said they were freed after nearly 24 hours, DW reported.

The Cockroach Janta Party is not a registered party. It demands the resignation of Chief Election Commissioner Gyanesh Kumar. Protesters say the voter-list review has removed about 130 million names and helps Prime Minister Narendra Modi's party. The Election Commission denies manipulating the lists.

Police refused permission for the rally. More than 25,000 police and security officers were deployed, and roads across the capital were barricaded, The Guardian reported. Media reports cited by the BBC said about 7,000 people were detained Saturday and released late at night. Opposition leaders and the YouTuber Dhruv Rathee were among those held.

After his release, Dipke called Modi an "embarrassment to India" in a social media post, France 24 reported. A temporary leader, Ajinkya Shinde, called for a protest in Mumbai on Sunday and said more cities "will follow." By early afternoon in Delhi there was no large crowd at the main protest site.

The movement began online in May. Its protests over exam paper leaks helped force India's education minister to resign in July. Key state elections are due in the coming months.

What we know: An Indian court ordered three Cockroach movement leaders released Sunday after police detained thousands of people in Delhi on Saturday.
What we don't: How many people were detained in all, with reports ranging from about 7,000 to tens of thousands.