Pakistani officials say ongoing ethnic and gang-related violence in Karachi has left at least 30 people dead since Wednesday in the southern port city.

Police say much of the violence has been focused in Karachi's southern Lyari neighborhood, a stronghold of the ruling Pakistan People's Party, where criminal gangs are known to operate.

The overnight attacks came after a series of fights Wednesday night killed at least 10 people, including a former lawmaker from the PPP.

Karachi, Pakistan's largest city, has seen a surge of violence in recent weeks.

Rights groups say more than 800 people have been killed in Karachi so far this year, with more than 200 dead in July alone.

Authorities say the killings are part of clashes between the main political groups, which represent two different ethnic communities. The political parties are also said to have links to armed criminal gangs.