A plane has crashed in hills north of the Pakistani capital, Islamabad, killing all 152 people on board.

The plane, an Airblue flight from Karachi to Islamabad, came down in the Margalla Hills.

Officials said the plane lost contact with the control tower minutes before landing. It is not known what caused the crash.

Pakistani TV showed images of smouldering wreckage on a foggy hillside, with helicopters overhead.

Imtiaz Elahi, chairman of the Capital Development Authority, which deals with emergencies, said the situation at the site of the crash was "heartbreaking".

"It is a great tragedy, and I confirm it with pain that there are no survivors," he told the Associated Press news agency.

The plane, reported to be an Airbus A321 with 146 passengers and six crew on board, is thought to have left Karachi at 0750 (0350 GMT).

Two Americans were among the victims, a US embassy spokesman told the Reuters news agency, but gave no further details.

Pakistan's Interior Minister Rehman Malik said at least five survivors had been taken to hospital, but local officials later said those reports were wrong.

Local TV footage showed twisted metal wreckage hanging from trees and scattered across the ground. A flight recorder has been found.

Officials said rescuers searching for survivors were digging through the rubble with their bare hands. The crash site, on a steep hill, has no roads.

"The plane is totally destroyed, the pieces and parts scattered over a large distance. Some parts of the plane are still burning. Some bushes have been burnt," said Express 24/7 television journalist Sabur Ali Sayed at the scene.

Aamir Ali Ahmed, a senior city government official, told Reuters: "It's a very difficult operation because of the rain. Most of the bodies are charred. We're sending body-bags via helicopters."

Airblue spokesman Raheel Ahmed told reporters that the crash was "an extremely tragic incident", adding that an investigation was being launched.

The BBC's Haroon Rashid in Islamabad saw the plane flying low over the capital.

"I was surprised to see the plane, because the area where I live is called a no-fly zone as it is close to some of Islamabad's most important official buildings, including President House and parliament," he said.

Other witnesses saw the plane flying towards the hills, and shortly after that heard a loud explosion and smoke billowing into the air.

Express 24/7 TV reporter Anjum Rahman said she saw the plane flying over the rooftops of houses where she lives.

"I wondered why the plane wasn't flying higher as it was flying towards the hill. Then within three or four minutes I heard a loud explosion," she told the channel.

Saqlain Altaf told Pakistan's ARY news channel that he was on a family outing in the hills when he saw the plane, looking unsteady in the air.

"The plane had lost balance, and then we saw it going down," he said, adding that he heard the crash.

Initial reports said the flight originated in Turkey, but this has not been confirmed. Later reports suggested it was a commuter flight.