A 22-year-old Indian climate activist has been arrested after sharing a document intended to help farmers protest against new agricultural laws.
Police said Disha Ravi was a "key conspirator" in the "formulation and dissemination" of the document.
The "toolkit", which suggests ways of helping the farmers, was tweeted by prominent activist Greta Thunberg.
Activists say Ms Ravi's arrest is a clear warning to those who want to show support to anti-government protests.
Tens of thousands of farmers have been protesting for more than two months over the laws, which they say benefit only big corporations.
The new legislation loosens rules around the sale, pricing and storage of farm produce which have protected India's farmers from the free market for decades.
The farmers' protests mark the biggest challenge India's Prime Minister Narendra Modi has faced. His government has offered to suspend the laws but the farmers want them replaced altogether.
What do we know about Disha Ravi's arrest?
Ms Ravi, one of the founders of the Indian branch of the Fridays for Future climate strike, was arrested by Delhi police.
In a statement posted on social media on Sunday, police said she had "collaborated" to "spread disaffection against the Indian State".
It said she was an editor of the document and had shared it with Swedish climate activist Ms Thunberg.
Officials said Ms Ravi would be held in custody for five days. No formal charges have been announced.
Police have said the toolkit suggested a conspiracy in the run up to a huge rally on 26 January, which saw protesting farmers clash with police.
"The call was to wage economic, social, cultural and regional war against India," Delhi Police Special Commissioner Praveer Ranjan said earlier this month.
"We have registered a case for spreading disaffection against the government of India - it's regarding sedition - and disharmony between groups on religious, social and cultural grounds, and criminal conspiracy to give shape to such a plan," he added.
Jairam Ramesh, a former minister and lawmaker for the opposition Congress party, called Ms Ravi's arrest and detention "completely atrocious".