Tuesday's blasts took place roughly 15 minutes apart in different areas of Karachi, Pakistan's economic hub [Reuters]

The Pakistani Taliban has attacked buses carrying navy officials in Pakistan's largest city, killing four people and wounding 56 others.

The roadside blasts took place roughly 15 minutes apart on Tuesday in different areas of Karachi, a southern port city that is Pakistan's economic heart.

Tehreek-e-Taliban spokesmen claimed responsibility for the attack by telephone from undisclosed locations. 

Police said the bombs targeting the buses in two different parts of Karachi were remote controlled.

A junior naval officer and a civilian female doctor were among those killed in the twin blasts, Commander Salman Ali, a spokesman for the Pakistan navy, said. 

The attacks followed the deaths of 15 people, including four children and two women, when a bus was set on fire in Balochistan, a province in southwestern Pakistan, late on Monday.

A senior government official said the incident happened in Sibi, a town about 160km east of the provincial capital Quetta, when the bus was parked near a roadside restaurant.

Ethnic Baluch fighters have waged a low-level campaign for decades for more autonomy and greater control of natural resources of their region. They frequently attack government installations and security forces.

Taliban threat

The Pakistani Taliban vowed to continue attacks on the country's military until it stops targeting the group in the country's northwest.

Zafar Hilaly, defence and foreign affairs analyst, laid the blame for the attacks squarely at the door of groups like the Pakistani Taliban.

"The killings are clearly the result of militant action. There are a lot of them in Karachi ... indeed Karachi is regarded as a haven for them," he told Al Jazeera.

"They come down from the frontier to recoup, plan ... and then they go back."

Analysts say that the attacks may be part of a wider campaign to hit security forces across the country.

"It appears to be part of the same militant campaign but I don't see any logic in targeting the navy because, unlike the army and air force, they are not  involved in any operations against the militants," Tasneem Noorani, a security analyst and former interior secretary, said.

"They may have targeted navy out of desperation because the other forces [air force and army] may have become very careful and are difficult to attack."

The attack on the military in Karachi was the first since 2004 when assailants ambushed a convoy escorting the Karachi army corps commander. The general escaped that attack.

In 2002, 11 French engineers and technicians working on the  construction of submarines for the Pakistani navy were killed, along with three Pakistanis in a suicide car bombing outside a hotel in Karachi.

This is the first time the navy have been attacked or targeted in Pakistan. Karachi is the main base for the navy.

Source: Agencies