Image copyright AFP

At least 31 people have died and around 170 are missing after a ferry collided with a cargo ship in the Philippines.

More than 600 survivors have now been rescued since the MV Thomas Aquinas sank after a collision with a cargo ship on Friday night.

Coastguard and military vessels helped with the rescue, but the operation has been hampered by rough seas.

The Philippines has a poor record for maritime safety, with scores of people dying in accidents every year.

'Strong impact'

The collision happened on Friday evening near the central city of Cebu - around 2km (1.2 miles) from the shore.

The MV Thomas Aquinas was carrying 715 passengers and 116 crew, according to the latest coast guard figures.

Media playback is unsupported on your device Media caption The BBC's Jonathan Head: Frightening ordeal for passengers

"The impact was very strong," Rachel Capuno, a spokesperson for the owners of the ferry, told local radio.

Survivors said hundreds of passengers jumped into the ocean as the ferry began taking on water and listing. The crew distributed life jackets.

Image copyright AP Image caption Life rafts floated alongside the cargo ship after the ferry sank Image copyright AFP Image caption Fishermen were covered in oil as they helped with the search Image copyright AFP Image caption Coast guard workers continued to look for bodies and any remaining survivors Image copyright Reuters Image caption The damage to the cargo ship was clearly visible previous slide next slide

Many of the passengers were asleep and others struggled to find their way in the dark, reports said.

One survivor, Jerwin Agudong, said he and other passengers jumped overboard in front of the cargo vessel.

"It seems some people were not able to get out," Mr Agudong told radio station DZBB. "I pity the children. We saw dead bodies on the side, and some being rescued."

It is believed 58 babies were among the passengers on board but it is unclear how many of them died.

Many of the survivors were sick from swallowing seawater and oil that is thought to have spilled from the ferry.

Rear Admiral Luis Tuason, of the coast guard, said more bodies had been found on Saturday and that the death toll would almost certainly continue to rise.

"Because of the speed by which it went down, there is a big chance that there are people trapped inside," he told AFP.

Another coast guard official told reporters that the cargo ship, Sulpicio Express 7, had 36 crew members on board, but it did not sink.

Passengers on the ferry had embarked at Nasipit in the southern province of Agusan del Sur.

The 11,000 tonne ferry was 40 years old, and operated by a Chinese-owned company called 2Go, reports the BBC's South East Asia Correspondent Jonathan Head.

The company became the largest ferry operator in the Philippines three years ago, following a merger of several smaller firms, our correspondent adds.

PHILIPPINE FERRY DISASTERS 1987: Dona Paz ferry sinks after colliding with a fuel tanker, 4,341 people die.

2008: The ferry MV Princess of the Stars capsizes during a typhoon, killing nearly 800.

Joy Villages, an official at the coastguard's public affairs office headquarters in Manila, told AFP it was too early to determine the cause of Friday's collision.

She said the Thomas Aquinas was a "roll-on, roll-off" ferry that transports vehicles and is commonly used in the Philippines.

Maritime accidents are quite frequent in the Philippine archipelago because of tropical storms, badly maintained passenger boats and weakly enforcedf safety regulations.

The world's worst maritime disaster in peacetime occurred in the Philippines in December 1987. More than 4,000 people died when the Dona Paz ferry collided with a tanker.