From the photos on twitter, it looks like it hit the only soccer field in town, landing between the field and the playground next to it. Hezbollah first claimed the attack, but now that there are 10 kids dead, and another several dozen kids injured they’ve backpedaled on it.
UPDATE: 10 dead, 6 in critical, 3 moderate, 4 light, and several dozen unadmitted injured people
Hardly an “attack on Beirut.” According to this it was an attack on a Hamas commander near Beirut.