Prosecutors said on Wednesday that they were seeking 18 months of pre-trial detention for Mr Castillo, who has been charged with rebellion and conspiracy.
Peru‘s supreme court met to consider the request but have suspended the session until Thursday.
Mr Castillo’s former vice president, Dina Boluarte, has been sworn in but the move has divided other Latin-American leaders and the upheaval has angered many Peruvians.
Authorities have said eight people, mainly teenagers, have died in clashes with the police – with rights groups claiming at least six were killed by gunfire.
Protesters have blocked motorways, set buildings alight and invaded airports.
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“We have agreed to declare a state of emergency throughout the country, due to acts of vandalism and violence,” said defence minister Alberto Otarola.
“This requires a forceful response from the government.”
‘We don’t want to return to that painful history’
President Boluarte has called for “peace” and suggested elections could be held a year from now – four months before her earlier proposal of April 2024.
The vote was originally slated for 2026, when Mr Castillo’s term would have ended.
“The only thing I can tell you sisters and brothers (is) to keep calm,” Ms Boluarte said.
“We have already lived through this experience in the 80s and 90s, and I believe that we do not want to return to that painful history.”
Her remarks recalled the years when the communist party’s insurgency presided over numerous car bombings and assassinations.
The group was blamed for more than half of the nearly 70,000 estimated deaths and disappearances caused by various rebel groups and a brutal government counterinsurgency response.