By Rayhan Demytrie
BBC News Central Asia correspondent
**An environmental activist sentenced to five years in prison in Turkmenistan was jailed on trumped-up charges, rights campaigners have said.**Andrei Zatoka was arrested for assault after an altercation with a stranger in a market - an incident campaign group Human Rights Watch said was staged.
It also said his trial was fixed and he was not allowed any legal defence.
Mr Zatoka has long claimed he is a victim of a politically motivated harassment by the Turkmen authorities.
His sentencing took place at a closed hearing in the city of Dashoguz, in northern Turkmenistan.
Human Rights Watch (HRW) has called for his immediate release.
“The trial of the activist violated international fair trial standards,” the US-based group said in a statement.
Reforms promised
Andrei Zatoka is an internationally renowned environmental activist who has been campaigning on ecological issues in Turkmenistan, formerly part of the Soviet Union.
He established an environmental protection group in the early 1990s but it was shut down by the authorities in 2003.
“The Turkmen authorities tolerate no dissent,” said Farid Tukhbatulin a co-founder of the group who now heads the Turkmen Initiative for Human Rights in Vienna.
“This is a message to a handful of other activists who are brave enough to work in Turkmenistan,” Mr Tukhbatulin told the BBC.
The Turkmen government was not available for a comment.
Natural gas-rich Turkmenistan is among the most repressive states in Central Asia.
President Kurbanguly Berdymukhamedov came to power in 2007 promising to open up his country and introduce reforms after years of isolation under Turkmenistan’s previous ruler, President Saparmurat Niyazov.
But critics say few genuine reforms have taken place and the restrictions on basic freedoms continue.
Vitaliy Ponamarev, from the Memorial Human Rights centre in Moscow, says that Andrei Zatoka, who was convicted in the past, became a symbol of reforms that never materialised.
"He was arrested under President Niyazov and his sentence was suspended when the new president came to power.
“There was hope that things would change. But nothing has changed. He has been sentenced again for nothing.”
Rights groups say the EU and the United States should do more to address the issue of human rights with the government of Turkmenistan.