An eight-year-old boy was killed Monday when a grenade was thrown into the apartment in Sweden where he was sleeping, police said, adding he was likely the victim of an underworld feud.

The child was sleeping in the living room of an apartment in the working class neighborhood of Biskopsgarden in Gothenburg, on Sweden's west coast, when an unidentified attacker threw a hand grenade through the window, police said in a statement.

At least five children and several adults were in the apartment at the time.

"One of the people registered at this address is a person convicted by a district court for murder" in a settling of scores between members of the Somali community in Gothenburg, police said.

In March 2015, armed men burst into a pub in the Biskopsgarden neighborhood, gunning down a man known to police and an innocent bystander in a spray of bullets.

Eight people were convicted earlier this month for the attack, and handed sentences ranging from seven years to life in prison.

According to local newspaper Goteborgs-Posten, which conducted a lengthy investigation of the vendetta, the pub shooting spree was the culmination of several violent incidents between rival gangs over the drug market.

While Sweden is generally a peaceful, safe country with low crime rates, police have had difficulty addressing violence in poorer neighborhoods in Stockholm, Gothenburg and Malmo.

In recent years, there have been grenade attacks, shootings and incidents of car arson.

The issue has been one of the main topics of Sweden's political debate this summer, as cars have been torched in the neighborhoods on an almost nightly basis.

The center-right opposition has called for 2,000 more police officers to be hired, while the leftwing government has proposed a series of crime prevention measures.