The unnamed girl died after she was struck by a stray bullet in the car park of a petrol station near Stockholm in the early hours of Sunday morning, according to local media.
The Expressen newspaper reported that two men linked to a criminal gang were the intended targets of the shooting.
Swedish police have launched an investigation into the murder.
National police chief Anders Thornberg told the TT news agency: “We will investigate and do everything in our power to bring the people behind this terrible act to justice.”
“We will collect witness statements, forensic evidence and all material that could help us move the investigation forward. But how successful we are also depends on those who know anything about the incident coming forward and helping us solve the crime,” he added.
Mr Thornberg added that authorities would tackle “increasingly serious violence in society”, while justice minister Morgan Johansson vowed “more police and harsher sentences” after the incident.
Meanwhile, opposition MP Johan Forssell said steps should be taken ”to make Sweden safer”.
Swedish police data shows that 20 people were killed in the first half of this year as a result of 163 shootings, while 334 shootings in 2019 led to 42 fatalities.
In comparison, 32 people were killed in shootings in England and Wales in the year up to March 2019, according to the Office for National Statistics (ONS).
Last year, Sweden established a special task force to counter gang violence, which has been growing in recent years.
There has been a large spike in bomb attacks in Sweden, an increase thought to be linked to gangs. There were 257 bomb explosions across the country in 2019, up from 162 the year before.