Russian gay rights activist Nikolai Alekseev says he was kidnapped and possibly drugged by Russian security forces who detained him for more than two days.
Mr Alekseev went missing on Wednesday evening from Domodedovo Airport in Moscow when he was due to catch a plane to Geneva. Friends received text messages from his phone saying he was in Minsk but did not believe they were from him.
He resurfaced in Moscow on Saturday and posted an account of the last few days on his website.
He wrote that he had passed through passport control at the airport and was under international law when he was informed by an official that his luggage had not been checked properly.
He says he was then handed to four men in civilian clothes who drove him to a police station in Kashira and was able to tell friends and the news agency Interfax he had been detained.
His phone was then confiscated, although he was able to use his iPad to discover where he was.
He said that after his phone was confiscated, his friends received messages purportedly from him, saying that he was in the Belarusian capital, would be applying for political asylum there and that he would give up his legal challenges against Moscow authorities in the European Court of Human Rights.
Mr Alekseev said that the four men called him homophobic insults and suggested his withdraw his legal challenges against Moscow for banning gay Pride marches.
He added then the men brought him a glass of water which he suspected to have been drugged. He said he "lost concentration, and felt some kind of emotional unresponsiveness".
He said that on Thursday evening, the men took him to Tula, which is 120 miles from Moscow and he feared he would be killed.
However, the men took him to the outskirts of the city and released him on Friday evening. As he did not have his passport, he caught a bus overnight back to Moscow.
According to a UKGayNews translation of his account, Mr Alekseev says he will sue Swiss Air Lines and Domodedovo Airport for allowing him to be taken by the men and will "demand a complete investigation into the basis of crimes against me in the form of illegal deprivation of freedom and kidnapping".
He added that to abandon the court cases would be a "betrayal" to those who have supported him and that he would not consider applying for asylum in another country.
While Mr Alekseev was detained, the French foreign ministry and a German politician raised concerns for him and demanded Russia guarantee his freedom.
The campaigner has been a thorn in the side of Moscow mayor Yuri Luzkhov for years over the administration's refusal to recognise gay rights.