The archipelago was plunged into chaos on Thursday when the Supreme Court called for the release of nine imprisoned opposition politicians, ruling that their trials were politically motivated and flawed.
The government refused to implement the ruling, prompting a wave of protests in the capital, Male, with angry clashes between police and demonstrators.
Yameen yesterday declared a state of emergency. Chief Justice Abdulla Saeed and another judge, Ali Hameed, were arrested hours after the government declared a state of emergency. No details were given about the investigation or any charges.
Nasheed, whose Maldivian Democratic Party functions from Colombo, asked for India's help.
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He urged India to "act swiftly" to resolve the crisis.
"President Yameen's announcement which declares a state of emergency, the banning of fundamental freedoms, and the suspension of the Supreme Court is tantamount to a declaration of martial law in the Maldives. This declaration is unconstitutional and illegal. Nobody in the Maldives is required to, nor should, follow this unlawful order," Nasheed said.
Nasheed also expressed concern over Yameen's deliberate delay in implementing the Supreme Court ruling to immediately release political prisoners.
Nasheed, 50, the country's first democratically-elected leader -- was sentenced to 13 years in jail on terror charges in March 2015 over the arbitrary arrest of chief criminal judge Abdullah Muhammed during his presidency.
He was granted asylum in the UK after he was authorised to seek medical treatment there amid mounting foreign pressure.
Nasheed was narrowly defeated in 2013 by President Yameen. Nasheed says his conviction on terror charges was politically motivated
The Maldivian government holds that Nasheed is convicted for a crime and is wanted in the Maldives to serve a jail sentence. Nasheed said he will seek UN support to ensure he is allowed to contest.