Ahmed Mansoor is appealing 10-year sentence over Twitter posts that authorities say breach cybercrime laws.

Prominent Emirati rights activist Ahmed Mansoor has filed a Supreme Court appeal in a bid to overturn a 10-year prison sentence handed to him earlier this year over several Twitter posts.

Mansoor was sentenced in May by Abu Dhabi’s Federal Appeals Court for “defaming the UAE through social media channels”.

A father of four, Mansoor was also fined one million dirhams ($270,000) for insulting the status and prestige of the UAE and its symbols, including its leaders.

Several international rights groups, including a number of United Nations human rights bodies, the EU Parliament’s Subcommittee on Human Rights, Amnesty International, and Human Rights Watch have condemned the move.

According to Joe Odell, the campaigns manager for the International Campaign for Freedom in the UAE (ICFUAE), since the instituting of the cybercrime law in 2012, there has yet to be a precedent where a rights activist has successfully appealed their sentence.

“Under new laws in the UAE, Mansoor is entitled to appeal the verdict,” Odell told Al Jazeera. “Since the appeal process is held in the same court, it is unlikely that the process will be a fair and independent one,” he added.

ICFUAE said that since the ruling, Mansoor’s health has deteriorated rapidly, and all his visitation rights have been suspended.

Odell added that Mansoor has also been denied access to a lawyer.

Furthermore, the activist’s exact place of detention remains unknown.

“His continued detention is in clear breach of Article 19 of the Universal Declaration of Human Rights, which guarantees the right to freedom of opinion and expression, to which the UAE is a signatory,” Odell said.

International pressure is key to overturning the case, he added.

“There must be more pressure generally from Western governments, international bodies and importantly the media to keep it in the public domain,” he said.

“The Emirati regime are very PR conscious, so are likely to respond to sustained international pressure.”

Mansoor’s case has been raised with Emirati authorities by the UK government and the European Union.

“Moreover, the UN Working Group on Arbitrary Detention, the UN Working on Enforced Disappearances, UN Special Rapporteurs and the EU Parliament have condemned his detention and called for his release,” Odell said.