|July saw Karachi's highest death toll in decades, with about 300 dead [EPA]
Police in Karachi, Pakistan's financial capital, have been ambushed by a group of gunmen, sparking violent battles in which four officers were killed and 40 wounded, officials said.
Late on Friday, the police commandos, dressed in plain clothes, were targeted in the eastern neighbourhood of Korangi, which has been immune from the political and ethnically linked violence that has swept through Pakistan's largest city.
"These policemen were in a van going on a raid on a tip-off when they were intercepted by armed men who started firing, injuring many policemen," senior police official Shaukat Hussain told AFP.
"The police returned fire and at least one attacker has been killed."
Television footage of the aftermath of the attack showed injured officers being carried by their colleagues and local residents into ambulances and private vehicles heading to hospital.
Series of violence
The attack comes as Karachi's police chief on Friday said the deadly violence had killed 52 people over three days.
Security was tight in Karachi as residents remained nervous.
"The situation is as bad as 50 families are devastated in 12, 24 hours. We don't know who are the killers? Where they come from? Where they go and hide?" Shakeel Ahmed, a resident, told Reuters news agency.
Much of the fighting erupted in and around the old district of Lyari, where spats between rival gangs have intensified in recent weeks.
Waja Karim Dad, a senior leader of Pakistan's ruling Pakistan People's Party (PPP), was among those killed on Wednesday, officials said.
The attacks happened as Karachi's main party, the MQM, said it was rejoining the national PPP-led coalition government.
"Most of the killings have resulted from clashes between criminal gangs operating in Lyari and surrounding areas," a senior police official said.
"It's not the kind of fighting that we saw last month; this is more of a gang war."
But police said turf wars between gangs dealing in drugs and extortion rackets were by no means a new development in Lyari.
"These gangs regularly clash and kill members and supporters of rival groups," the senior official said.
Political gang warfare
Al Jazeera's Kamal Hyder said the killings were directly related to gang warfare conducted with the patronage of the country's political elite.
The killings in Karachi have continued despite efforts to reconcile its warring political factions.
Security officials say this is because the killers are being protected by senior politicians.
They say the violence is being used to stoke recently ignited ethnic passions both for political gains and as a means by criminal gangs to fight turf wars behind the facade of political activism.
"Everything boils down to politics," said Hyder.
A city of more than 18 million, Karachi has a long history of violence, and ethnic, religious and sectarian disputes and political rows can often explode into battles engulfing entire neighbourhoods.
Pakistan's interior minister earlier this month vowed to restore peace in the city after a fresh bout of violence and warned of stern action against any group intent on using violence.
Hundreds of additional police and paramilitary troops were deployed in Karachi last month to quell the unrest.
About 300 people were killed in July, making it one of the most deadliest months in almost two decades. Human rights groups say 800 have been killed since the start of the year.