(Adds Balbay remarks following release, background)
ISTANBUL, Dec 9 (Reuters) - Journalist and elected parliamentarian Mustafa Balbay was freed from prison on Monday pending appeal after Turkey's Constitutional Court ruled his pre-trial detention period of more than four years had violated his rights.
Balbay was among 275 defendants including an ex-military chief, retired officers, academics, journalists and opposition politicians given mostly long prison terms in August over an alleged ultra-nationalist plot to overthrow Prime Minister Tayyip Erdogan's Islamist-rooted government.
The Constitutional Court ruled last week that the four years and nine months Balbay spent in prison pending trial had violated his rights to freedom and representation of the people as an elected parliamentarian.
Balbay, a member of the main opposition Republican People's Party's (CHP), was sentenced to almost 35 years in prison. He had denied any role in the "Ergenekon" conspiracy network.
Defence lawyers have appealed against the guilty verdicts in the marathon, five-year-long Ergenekon trial but a final Constitutional Court decision is not expected before 2015.
In initial remarks upon his release from an Ankara prison, Balbay said he expected to take his oath for the parliamentary seat he won in 2011 on Tuesday. He had not been able to do so because he had been imprisoned since 2009.
"I will take my oath tomorrow afternoon probably, and will continue to fight against all injustices and unlawfulness until the end of my life," a cheerful Balbay said, hugging his wife and fellow CHP lawmakers.
"I feel responsible, like it was me who closed the doors on tens and hundreds of those who remain in prison seeking their rights. With my most sincere feelings, I hope that my release is a new beginning for all of them," Balbay told scores of supporters gathered in freezing cold, waving Turkish flags.
If the Court of Appeals rejects Balbay's request for his conviction to be quashed, he may have to return to prison even though as a parliamentarian he would enjoy immunity from prosecution.
There are six other MPs jailed in Turkey - five from the pro-Kurdish Peace and Democracy Party (BDP) suspected of links to the militant Kurdish separatist PKK movement, and one, a former soldier, from the Nationalist Movement Party (MHP) over an unrelated coup plot.
Balbay's release could set a precedent for the jailed BDP deputies, lawyers said. But the MHP deputy has already lost an appeal to the higher court, leaving him no chance of release under the ruling that freed Balbay. (Writing by Ece Toksabay; Editing by Mark Heinrich)