A wave of bloody attacks by motorcycle gangs left one dead and eight wounded in Jakarta over the weekend as police scramble to crack down what is becoming a growing problem in many Indonesian cities. Four teenagers were attacked while riding their motorcycles on Jalan Danau Sunter in North Jakarta early Saturday morning, police said. Soleh, 17, was killed in the fight. Three of his friends, Zaenal, 19, Reza, 16, and Ardin, 19, suffered injuries. The four were reportedly riding their motorcycles after watching illegal street races in Kemayoran, Central Jakarta. Less than 24 hours later, a gang of bikers attacked another group of riders on Jalan Benyamin Sueb in Kemayoran. Five were stabbed and a motorcycle was torched in the melee, police said. In both instances, the attackers allegedly wore white marks under their eyes, police said. “Investigators have found an indication that the groups committing the attacks in Sunter and Kemayoran are connected,” Jakarta Police spokesman Sr. Comr. Rikwanto said in Jakarta on Monday. Police responded by forming a special investigative team with officers from precincts in North and Central Jakarta to look into the incidents. Police suspect the attacks were motivated by revenge and related to Jakarta's underground street racing scene. Biker gangs have become a pressing concern in many Indonesian cities, spurred, in part, by the popularity of motorcycles. The members are frequently involved in seemingly random and, at times, fatal mob attacks, police said. On Thursday, another gang of bikers killed Rahmad Gunawan Nasution, a member of a rival gang, in front of Plaza II Pondok Indah Mall in South Jakarta. The alleged leader of that attack, Azwar Anas, has been arrested by police. Police did not say whether the motorcycle gangs in South Jakarta are related to those operating in Central and North Jakarta.