A Tunisian court on Tuesday ordered blogger and anti-Islamist activist Sofiane Chourabi to pay a 104 dinar (52 euro/$67) fine for drunkenness and indecency during Ramadan, he told AFP.
Chourabi said he would appeal against the conviction, insisting the charges against him were trumped up by the Islamist-led government.
The court ordered Chourabi and his journalist friend Mehdi Jelassi to pay 100 dinars each for indecency and four dinars each for drinking alcohol in public during the Muslim fasting month of Ramadan.
The two men were arrested at the beginning of August for allegedly drinking alcohol on a beach near Menzel Temime, south of Tunis, and initially faced a six-month jail sentence.
"I will appeal the court's decision because it confirms accusations which I totally reject and deny," Chourabi told AFP.
The blogger was a vocal opponent of president Zine El Abidine Ben Ali but since the veteran strongman's overthrow early last year has been strongly critical of the Islamist Ennahda party that leads the governing coalition.
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"It is an unfair trial, completely made up and baseless. It is about intimidating the opponents of Ennahda's policies," Chourabi said at a hearing in early October.
He said a confession he made in August was made "under police pressure."
Amnesty International criticised the court decision.
"Restrictions of individual freedoms in the name of public order must be necessary and proportionate, and must never be used as an excuse for prosecuting government critics and other political activists," said the watchdog's deputy Middle East and North Africa programme director Hassiba Hadj Sahraoui.
"These convictions must be quashed, and the Tunisian authorities must refrain from prosecuting individuals who freely exercise their fundamental rights, including their right to freedom of expression."
The trial comes at a time of heightened concerns in Tunisia over freedom of expression, and follows a spate of attacks by hardline Salafist Muslims over the summer on targets deemed un-Islamic.
The case was brought against Chourabi by a man who claimed he was the victim of a "moral offence" because of the alleged incident.