The death toll from a pair of factory fires that broke out in Pakistan's two biggest cities has risen to 314 people.

Many of the people died because they were unable to escape buildings that lacked emergency exits and basic safety equipment, such as alarms and sprinklers.

The more deadly of the two blazes, which both erupted last night, was at a garment factory in the southern city of Karachi.

The death toll in Karachi has been reported to be 289 people, one of the worst industrial accidents in Pakistan's 65-year history.

A spokesman for the fire service said most of the deaths were caused by suffocation as people caught in the basement were unable to escape when it filled with smoke.

Workers on higher floors of the five-storey building struggled to make it out of windows that were covered with metal bars.

Many were injured when they jumped from the building, including a 27-year-old pregnant woman who was injured in the fall.

Police raided buildings in different parts of Karachi searching for the factory owners.

A fire also swept through a four-storey shoe factory in the eastern city of Lahore, killing 25 people.

The factory was illegally set up in a residential part of the city.

The fire broke out when people in the building were trying to start their generator after the electricity went out.

Sparks from the generator made contact with chemicals used to make the shoes and ignited the blaze.

A preliminary provincial government report concluded that the closure of the emergency exits led to the deaths and labour and safety regulations were not applied, government sources said.