Rio De Janeiro , Brazil ( CNN ) -- Violence including clashes between police and drug gangs in the slums of Rio de Janeiro has killed 23 people since Sunday , with 188 people arrested or detained so far , military police said Thursday . It was not immediately clear whether all the dead were gang members or whether civilians and police were among the fatalities . The continuing unrest stems from the transfer of prisoners from local institutions to federal lockups in other states , the government-run Agencia Brasil news outlet reported , citing Rio de Janeiro Public Security Secretary Jose Mariano Beltrame . Some of the prisoners being transferred ordered the violence by drug gangs , Beltrame said . Also factoring into the situation was a police effort to remove some drug gang members from Rio 's crime-ridden slums , called favelas . According to the military police , two police officers have been hurt in the unrest , with 66 people arrested and 122 others detained . In addition , 37 vehicles have been torched : 27 cars , two vans , seven buses and a truck , the military police reported . Earlier , officials said the drug gangs also shot up a police station . At least 47 public schools and 10 nurseries suspended classes Thursday , Agencia Brasil reported . Beltrame said two rival gangs joined forces to launch the attacks . The security chief also said he mobilized all police in the city to try to restore order and to step up police presence in 17 of Rio 's slums . Agencia Brasil reported that the nation 's Army was on high alert but had not been called in to bolster police efforts . The news agency also said Brazil 's Marine Corps sent armored vehicles , weapons , ammunition and night-vision goggles for use by Rio de Janeiro security forces at the request of Rio de Janeiro State Gov . Sergio Cabral . On Tuesday , Brazilian President Luiz Inacio Lula da Silva told CNN affiliate TV Record that he had instructed his justice minister `` to attend to Rio de Janeiro with whatever he needs . '' Officials are concerned about crime in Brazil as the nation prepares to host the 2014 World Cup soccer tournament and the 2016 Summer Olympics , which will be held in Rio . Journalist Luciani Gomes contributed to this story .
NEW : 188 people have been arrested or detained , military police say . Comment: The violence involving drug gangs started with a transfer of prisoners , an official says . Two rival drug gangs collaborated to launch the attacks , the official says .