Top leaders of India’s “cockroach” youth movement were detained on Tuesday after they jumped barricades to enter the grounds of a historic observatory popular for protests, chanting slogans demanding the chief election commissioner’s resignation over a controversial revision of voter lists.

Supporters of the Cockroach Janta Party (CJP) and opposition groups have held almost daily protests this month to demand commissioner Gyanesh Kumar’s resignation over the revisions critics say favour Prime Minister Narendra Modi’s Bharatiya Janata Party (BJP).

The Election Commission has denied favouring any party and said wrongly deleted voters can re-enrol, while the BJP has accused rivals of trying to undermine ⁠democracy by wrongly questioning legitimate electoral processes.

Thousands joined a protest march by opposition groups on Monday, after a clampdown foiled CJP plans for a weekend demonstration, with police detaining thousands of protesters, including CJP leaders.

Delhi Police announced on Monday that the Jantar Mantar open air observatory, in the national capital’s central business district, was no longer designated as an official protest site, and said three new venues had been identified.

The CJP said its leaders Ashutosh Ranka, Saurav Das, and Ajinkya Shinde were among about 20 volunteers who “sneaked” inside the observatory to “reclaim” it and were detained.

“You cannot denotify the resistance,” founder Abhijeet Dipke said on X after their detention.

Biggest political challenge for Modi

A CJP livestream showed about a ⁠dozen volunteers jumping a gate and barricades to reach the site, where they waved the Indian flag and chanted slogans before police detained them.

Delhi Police did not immediately respond to a request for comment.

The youth movement, which has mobilised protests in recent months against issues ranging from government school infrastructure to jobs, is among the biggest political challenges to Modi and his BJP ⁠in his 12 years in power.

A weeks-long sit-in by its supporters at Jantar Mantar earlier this year forced the resignation of Education Minister Dharmendra Pradhan over exam paper leaks.

The latest protests erupted after the Indian Express newspaper reported last month that Kumar’s two deputies ⁠raised several concerns internally about voter list revisions, registration procedures and digital systems.

The change, which started last year, removed over 130 million names – more than the population of Japan – from voter lists, including 28 million who died, 63 ⁠million who relocated, and 30 million who could not be traced.

Opposition parties allege the deletions disproportionately affect Muslim voters and other minorities, who are unlikely to support the Hindu nationalist ruling party — allegations the poll panel and BJP reject.