Shootings stir more tension in fearful Florida city SANFORD, Florida (Reuters) - Two drive-by shootings this week have ratcheted up tensions in this central Florida city, which has been rocked by protests and anger over the killing of unarmed black teenager Trayvon Martin just over a month ago. Sanford police said three people, including a pregnant woman, were injured in the latest shooting in a predominantly black district of the city early on Wednesday morning. The victims were all identified as African Americans by police spokesman Sergeant David Morgenstern, as was a 17-year-old male who was shot and seriously injured in a drive-by in the same neighborhood before dawn on Monday. No arrests have been made in either of the drive-by shootings, and the victims have not been identified by name. But the latest was believed to involve a burst of automatic gunfire, police said. Unlike the 17-year-old, who is recuperating from the wounds he suffered on Monday, the trio of victims on Wednesday all had non-life threatening injuries, police said. The shootings occurred just blocks from where civil rights activists and local community leaders marched on Sanford Police Department headquarters last weekend to demand the arrest of George Zimmerman, the white Hispanic neighborhood watch volunteer who shot 17-year-old Martin on February 26. Police have not arrested Zimmerman, largely because Florida's so-called "Stand Your Ground" law requires them, without clear evidence to the contrary, to accept Zimmerman's claim that he acted in self defense when he shot and killed Martin with a gunshot to the chest. But protesters contend that Sanford police and other local officials failed to charge or arrest Zimmerman because he was the light-skinned son of a former magistrate judge from Virginia. The victim, a black youth from Miami, was singled out as suspicious, critics say, simply because he was spotted walking alone through the rain in a gated community where no one knew his name. The racially charged case has ignited a firestorm of controversy and Sanford Mayor Jeff Triplett is among those who fear that public protests over the killing, all of them peaceful so far, could turn violent. "I don't know what tomorrow will hold or the next day," Triplett told Reuters on Tuesday. "That's one of the what ifs that we're all sitting on right now," he said, when asked about the potential for violence. The area where the shootings broke the pre-dawn silence on Monday and Wednesday, just a block apart from each other, has been described by police as a well-established trouble spot in a city of 53,000 where dozens of shootings are reported every year. "Sanford is a small town with big city problems," Morgenstern said on Tuesday, when asked about crime statistics in the city with just 119 active duty police officers. "Sanford is a difficult area to police," he said. He stressed that Sanford had just four homicides or murder cases in 2011, however, and that Martin was the only reported killing so far this year. Reporting By Tom Brown; Editing by Vicki Allen