Here are the latest developments in this story:
"My sincere appeal to the people of Gujarat to maintain peace and not to indulge in activities disrupting law & order across the state," Chief Minister Anandiben Patel tweeted.
As news of Mr Patel's detention spread, cases of arson, allegedly by the young leader's enraged supporters, were reported from areas in Ahmedabad which have a large population of Patels, the community that Hardik Patel belongs to. The district administration has ordered the closure of schools today.
Incidents of arson have also been reported from the city of Surat, where Mr Patel had led a massive Patel or Patidar rally last week. Curfew was declared in two areas. Curfew was declared in parts of Mehsana district too, after a mob stoned the house of minister Rajni Patel.
At about 9 pm, the police lathi-charged a large crowd still present at the GMDC ground, where Hardik Patel had today led a mega-rally. Mediapersons were injured in the police action and equipment was damaged.
Mr Patel and five other leaders were detained. The police said he did not have permission to stay on at the public grounds after the rally. All of them were later released.
Hardik Patel had during the rally announced a 48-hour hunger strike. He is the face of a massive agitation to demand reservation in government jobs and colleges for the wealthy and politically influential Patels.
In a hard-hitting speech, the 21-year-old warned the BJP government in the state, "In the next (Gujarat) election in 2017, the lotus (BJP symbol) will not bloom if our needs are not met."
The Patels have for decades been loyal supporters of the BJP. But Chief Minister Anandiben has said they cannot be added to the list of castes entitled to quotas because Gujarat has hit the cap of 50 per cent reservation ordered by the Supreme Court.
In the afternoon about 60,000 of Hardik Patel's supporters followed him from the rally venue to the city collector's office to present a charter of demands. They clashed with a group that opposes reservation for Patels and the police had to use teargas to control the mob.
Other castes who benefit from reservation are opposed to the Patels' demand. These groups too held a rally in Ahmedabad on Sunday to amplify their opposition.
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