The accident occurred at Igandu, in the central Dodoma region, about 400 kilometres (250 miles) west of Dar es Salaam at about 0830 (0530 GMT).

The way the coaches are piled on top of each other, from far away you would think it is a multi-storey building

Prime Minister Fredrick Sumaye

Reports say that the passenger train, travelling from Dar es Salaam to the north-western town of Kigoma, was climbing a hill when it rolled backwards into the path of the goods train and went off the tracks.

"At least 200 people are dead but we fear there could be more," said Dodoma Regional Medical Officer John Kitimba, who is in charge of the rescue effort.

One survivor, John Maganga, 32, told the Reuters news agency that the train had started rolling backwards at high speed.

"The driver left the engine and ran into the cabins telling people to close the windows and shouting that the train was out of control," he said.

Driver escaped

The driver reportedly jumped off the train before the collision, suffering only minor injuries.

Isaac Mwakajila, assistant director-general of Tanzania Railways Corporation, said the train had suffered a mechanical fault on the hill.

The driver left the engine and ran into the cabins telling people to close the windows and shouting that the train was out of control

Survivor John Maganga

"The train went off the railway tracks backwards and smashed into another train behind it going in the same direction. It had 22 cabins and 21 of them fell off the rail tracks," he told Reuters.

Witnesses said hundreds of people had been injured.

"The badly injured so far are about 800," said Daniel Musangya, a journalist working for African Rural Press in Action.

Hospital overwhelmed

The injured were transferred to Dodoma hospital where the doctor in charge, Jacob Chembela, said the situation was desperate.

More than 200 patients, many suffering from broken limbs and head and chest injuries, were being treated at the hospital, he said.

"We are receiving more people... we are trying, we are doing our best but we are stretched with little equipment (to work with)," Dr Chembela said.

Health Minister Anna Abdallah said that a plane carrying doctors had left Dar es Salaam for Dodoma.

Cries of the trapped

But more than 10 hours after the crash, as darkness fell, people trapped inside the wreckage could still be heard crying for help, Betty Mkwasa, a reporter with Independent Television, told the Associated Press.

Rescuers do not have the heavy equipment needed to cut through the twisted steel to free those trapped, she said.

Parliament was in session in Dodoma at the time of the crash and Prime Minister Fredrick Sumaye went to the scene along with the Minister of Transport, Mark Mwandosya.

Ministerial cars were used to help transfer some of the injured to hospital.

"The way the coaches are piled on top of each other, from far away you would think it is a multi-storey building," Mr Sumaye told parliament after visiting the scene.

Mourning period

Mr Sumaye has declared two days of national mourning.

Rail officials said that at least 300 people were on the train when it left Dar es Salaam, but it was not known how many were on board when it crashed.

One report says the number could have been as high as 1,000.

Last month, nearly 200 people died in Mozambique when carriages from a passenger train ran down a hill and collided with a cargo train.