The Maldives High Court on Sunday dismissed former president Mohamed Nasheed's appeal against his 22 February arrest order.
Nasheed's Maldivian Democratic Party (MDP), now the main opposition, declared it will launch a nationwide civil disobedience campaign to secure his freedom.
As pro-Nasheed supporters gathered across the capital to protest his arrest and sentencing, Maldives President Abdulla Yameen said the court order should be respected.
He said Nasheed had a constitutionally guaranteed right to appeal, should he choose to do so, in line with Maldivian laws.
"The government calls on its international partners to engage constructively, based on mutual respect and dialogue in consolidating and strengthening democratic values and institutions in the country," said Yameen in a statement issued by his office.
The high court threw out Nasheed's appeal as he refused to enter the courtroom for the case's first hearing to protest the hearing not being open to the public.
Nasheed's legal team had requested that the court hold an open and public hearing. However, only members of Nasheed's legal team and family were allowed inside.
Quoting sources, a local news site said Nasheed refused to enter the courtroom after his request was turned down.
Nasheed was on Friday sentenced to 13 years in jail on charges of terrorism by the criminal court for his role in the January 2012 military detention of senior judge Abdulla Mohamed when he was president (See: India unhappy at sentencing of Maldives ex-President Nasheed).
The MDP National Council, in a resolution passed Saturday night, said it does not accept the court's verdict.
The terrorism conviction effectively bars Nasheed from contesting the presidential elections in 2018.
Stressing that Nasheed will remain the party's president and 2018 presidential candidate, the MDP said the party has decided to launch a nationwide civil disobedience campaign to free him.
MDP spokesman Hamid Abdul Ghafoor said Nasheed was repeatedly denied legal representation and the right to appeal.
He alleged that Nasheed's defence witnesses were prevented from deposing and prosecution witnesses were routinely coached by the judges and police.
Nasheed's legal team resigned last week, saying that the court had refused them proper time to prepare a defence.
Nasheed was elected to office in 2008. In February 2012, he was ousted in a coup (Protests rock Maldives' parliament, MDP blocks president's opening address).
In another development, prominent lawyer Shaheen Hameed, a relative of President Yameen, contended that Nasheed's trial was not conducted in a transparent and impartial manner and normal court procedures had not been followed.
"In my opinion, president Nasheed's terrorism trial was not fair and just. And another trial on (former defence minister Col. (retd) Mohamed) Nazim is being conducted in the same manner," he told reporters, according to Channel News Maldives.
"It will result in the loss of public trust in justice system. This is not a good thing for our country," said Hameed, who was deputy speaker of the People's Special Majilis tasked with drafting the new Constitution.
The European Union has said Naheed's conviction "raises very serious questions about due process of law and risks undermining people's trust in the independence of the judiciary". It called on all sides in Maldives to act responsibly and uphold constitutional freedom.
Neighbour India, in a statement on Saturday, voiced deep concern at the developments in Maldives and said it is monitoring the situation closely.
Human rights group Amnesty International has termed the conviction "deeply flawed" and a "politically motivated travesty of justice".
The US embassy in Sri Lanka also said it was "particularly troubled" by reports that the trial was not in line with Maldivian law and the country's international obligations.
The Human Rights Commission of Maldives has noted that during the criminal court proceedings against Nasheed on charges of terrorism, "there were concerns regarding the due process of law, in that certain rights as stipulated in the Constitution as well as in the International Covenant on Civil and Political Rights were not fully ensured".
Britain has also voiced concern that the trial had not been conducted in a transparent and impartial manner or in accordance with due legal process.