Bomb in Downtown Karachi Kills at Least 15

The Associated Press contributed to this report

Militants attacked a police compound in the heart of Pakistan's largest city on Thursday with a hail of gunfire and a massive car bomb, leveling the building and killing at least 15 people, authorities and witnesses said.

The gang of around six gunmen managed to penetrate a high-security area of Karachi that is home to the U.S Consulate, two luxury hotels and the offices of regional leaders. While no stranger to extremist violence, Karachi has not witnessed this kind of organized assault in recent years.

It was the first major attack against a government target outside the northwestern tribal regions for several months, showing the reach of Islamist militants seeking to overthrow the U.S.-allied government despite efforts to crack down on them over the last three years.

The gunmen first opened fire on the offices of the Crime Investigation Department before detonating a huge car bomb, said Sindh Home Minister Zulfiqar Mirza. The building has a detention facility that was believed to be holding criminals, and possibly militants.

The CID takes the lead in hunting down terrorists in Karachi. Earlier this week, the agency arrested six members of the militant Lashkar-e-Jhangvi group. The suspects were presented before a court earlier Thursday.

The attack, which targeted a compound housing the offices and some residential quarters of police investigators, renewed fears of the Taliban continuing their campaign to destabilize Pakistan - a nuclear-armed country and a key U.S. ally in the war against terror.

"This is definitely the work of TTP [Tehreek-e-Taliban Pakistan]," said a Karachi based intelligence official who spoke to CBS News on condition of anonymity. "We had reports for some time that the TTP were positioning themselves to strike at a major target."

"The attack bears the handprints of the Taliban," said the official, who declined to give further details.

Imran Ahmed, a rescue worker said, several people were still trapped in a two to three story apartment building in the area, whose front entrance collapsed.

"We are trying to make sure that we are able to rescue these people. I can't tell how many people are stranded but there could be more than a few," Ahmed told CBS News.

Shireen Khan, a middle aged woman slightly injured limped along a sidewalk as she cursed the Taliban. "I wish, these Taliban have their mothers, sisters, wives and daughters similarly injured. Only then, they (Taliban) will know what it is like to injure other people" Khan said.

In Islamabad, the Pakistani capital, a senior western diplomat said, the choice of the target near two five-star hotels once again underlined the difficulty of ensuring security in a congested neighborhood. Karachi, a city with a population of more than 17 million has seen previous terrorist bomb attacks including those targeting locations close to the site bombed on Thursday night.

"Pakistan has a very major challenge. This country has an active presence of militants. You can't screen each and every one person going through congested cities with explosives to blow a location" the diplomat told CBS News.

Suspected militants detonated a car bomb in the heart of Pakistan's largest city on Thursday,

The blast was heard several kilometers away in this city of 14 million people. It destroyed much of the several-story police building, damaged nearby houses and left a 10-feet (three meter) wide crater in the road. The U.S. Consulate was around a mile (1.5 kilometers) from the blast and was undamaged.

"We heard different kinds of firing for several minutes and then a deafening explosion," said Ali Hussain, who was covered in dust. "The roof of our house collapsed."

TV footage showed bloodied victims leaving the scene and security officers searching through the debris of the police building.

Dr. Seemi Jamai said 10 bodies had been brought to a nearby hospital, along with 90 injured.

Pakistan is battling Islamist militants with links to al Qaeda that are trying to overthrow the U.S.-allied government. The insurgents have repeatedly bombed government, police and Western targets over the last three years, including in Karachi.