HAVANA, July 21 (Reuters) - An anti-government hip hop song by some of Cuba"s most popular musicians in exile became the anthem of the unprecedented protests that rocked the Communist-run country last week. Now the visual artist who filmed the Cuban section of the videoclip for "Patria y Vida" ("Homeland and Life"), Anyelo Troya, 25, has been sentenced to a year in prison, according to relatives. He was charged with instigating unrest, they said, after attending a demonstration in Havana. Rights activists say this is just the start of what they predict will be a wave of summary trials of hundreds of people detained during and after the unusual protests on July 11 and 12 that the government has blamed on U.S.-backed counter-revolutionaries. "They took him to trial without defense or lawyer or anything," Troya"s mother Raisa Gonzalez told Reuters after witnessing his sentencing in what she called a collective trial of around a dozen people. The Cuban Foreign Ministry"s International Press Center, which fields all requests from foreign journalists for comment from state entities, did not immediately reply to request for comment on the cases mentioned in this article. Authorities confirmed on Tuesday they had started the trials of those detained on charges of instigating unrest, committing vandalism, propagating the coronavirus pandemic, or assault, charges that could carry prison sentences of up to 20 years. "There are people who will receive the response that Cuban legislation allows for, and it will be energetic," President Miguel Diaz-Canel said on state television last week. He promised there would be due legislative procedure. But Gonzalez said she was not informed of her son"s trial in time and when she arrived at the court with her lawyer, he had already been convicted. The trial was denounced by Amnesty International and Human Rights Watch (HRW) for taking place without proper defense or due process. Troya had already been under heightened vigilance for his participation in the song, whose headline is a twist on the revolutionary slogan "Patria o Muerte" ("Homeland or Death"), his mother said. Javier Larrondo, a representative of the human rights organization Cuban Prisoners Defenders, said authorities would likely lock up the most charismatic and effective opposition leaders, who lately have often been young artists, whether or not they were at the protests. "We will have hundreds of political prisoners in just two weeks," he said. The protests against Cuba"s worst economic crisis in decades and curbs on civil liberties first erupted ten days ago in a small town before spreading throughout the country. By the evening of day two, they appeared to have dissipated amid heavy security operations and internet disruptions. The government blamed mercenaries exploiting frustrations with hardships caused by U.S. sanctions. Exiled rights group Cubalex, which has established a spreadsheet of those detained that it updates every day as new reports come in, says more than 500 Cubans appear to have been detained during the protests or afterwards. It said the tally was likely higher, but some families may fear reporting the arrest of relatives in case of reprisals such as losing their state sector jobs. Some of those detained, like theater director Yunior Garcia, have been released to house arrest. "I have four officials in front of my door preventing me going out," Garcia told Reuters, which observed the officials. "When I go to buy food or cigarettes, one of them goes with me to keep a close eye on me." #SOS CUBA The majority of those detained have been kept incommunicado, while the location of some is still unknown, said Cubalex and HRW, based on interviews with relatives. Cubans have been posting photos of people they say they cannot locate or sharing stories of detentions on a Facebook group called "Disappeared #SOSCuba" with more than 10,000 members. "We went from police station to police station looking for her," said Alberto Betancourt of his sister, a stay-at-home mother-of-two who was detained at a protest in Havana. He located her after six days. "They won"t let me speak to her," he told Reuters, holding back tears. "But she"s not a criminal. She just let herself be swept up in the crowds." Cuban interior ministry officials denied on Tuesday that anyone was missing and said a list of detainees circulating - they did not specify which - was manipulated and included people who were never detained. The detained include high profile dissidents like Luis Manuel Otero Alcantara, who also featured in "Patria y Vida," and Jose Daniel Ferrer, the leader of the country"s largest opposition group. They also include ordinary citizens and bystanders, families and rights groups say. Many of those detained had been beaten or mistreated by security forces or rapid-reaction brigades - government-organized bands of civilian recruits, said HRW senior researcher Juan Pappier. Used to quiet streets, Cubans have been shocked over the last week by images of violence that have emerged on social media: security forces and bands of stick-wielding people in civilian garb beating protesters, as well as protesters throwing stones at police and overturning police cars. Diaz-Canel said last week "maybe there will be a need for apologies to anyone who, in the middle of all the confusion, has been mistreated," and defended security forces" actions to re-establish "peace."