STOCKHOLM (AP) — Three people were killed overnight in separate incidents in Sweden as deadly violence linked to a feud between criminal gangs escalated.

Late Wednesday, an 18-year-old man was shot dead in a Stockholm suburb. Hours later, a man was killed and another was wounded in a shooting in Jordbro, south of the Swedish capital.

Early Thursday a woman in her 20s died in an explosion in Uppsala, west of Stockholm. The blast, which damaged five houses, is being treated by the police as a murder. Swedish media said the woman who died likely was not the intended victim and that the target was the house next door.

Swedish broadcaster SVT noted that the two fatal shootings brings the death toll from gun violence in September to 11, making it the deadliest month for shootings since police started keeping statistics in 2016.

It was not known whether the shootings or the blast were related to each other but Swedish media said at least two of the three events were somehow connected to a feud between criminal gangs, a growing problem in Sweden with drive-by shootings and bombings.

Speaking Thursday on Swedish broadcaster TV4, Swedish Justice Minister Gunnar Strömmer said “it is a deeply tragic development. I understand that people feel anger, fear and sadness.”

Two gangs — one led by a Swedish-Turkish dual national who lives in Turkey, the other by his former lieutenant — are reportedly fighting over drugs and weapons.

Four people have been detained on suspicion of complicity in the fatal shooting in Jordbro. Police said that two people have been arrested over the Uppsala explosion, which was so violent that the facades of two houses were blown away.

Earlier this week, two powerful explosions ripped through dwellings in central Sweden, injuring at least three people and damaging buildings, with bricks and window sections left spread outside.

Sweden’s center-right government has been tightening laws to tackle gang-related crime, while the head of Sweden’s police has said that warring gangs have brought an “unprecedented” wave of violence to the country.

Earlier this week, Strömmer reiterated that Sweden will increase the penalty from three years to five years for possessing explosives without a permit as of April 1 when new legislation enters into force.

Magadalena Andersson, the leader of the main opposition party, the Social Democrats, told Swedish radio SR that the military could be performing certain functions to free up police by carrying out some transportation and guard functions. Strömmer said that it was “not relevant to deploy the military,” but that he was prepared to listen to all parties when it comes to solving the wave of violence.