* Government officials fear death toll may rise
* Oxygen pumped into mine, where hundreds trapped
* PM Erdogan cancels trip to Albania after the disaster
* Power outage cuts communications with miners (Updates toll, adds Erdogan comments, energy minister)
By Humeyra Pamuk and Orhan Coskun
ISTANBUL, May 13 (Reuters) - An explosion followed by a fire in a coal mine in western Turkey killed 157 miners and trapped hundreds more on Tuesday, a provincial mayor said, in what appeared to be the country's worst mining accident in years.
Rescue workers pumped oxygen into the mine to try to keep those still trapped by the blaze alive as thousands of family members and fellow workers, clamouring for information, gathered outside the town's hospital, held back behind police lines.
The blast in the power unit of the mine in Soma, around 120 km (75 miles) northeast of the Aegean coastal city of Izmir, triggered an electricity outage, making the elevators unusable and leaving hundreds of miners stranded underground.
It was not immediately clear if the fire had been isolated.
Cengiz Ergun, mayor of Manisa province where Soma is located, said nearly 600 workers were underground at the time of the explosion. Citing health officials at the entrance to the mine, he told broadcaster CNN Turk that 157 miners had died.
Government officials told Reuters 104 people had been confirmed dead and 54 injured, but said the toll was likely to rise. Turkey's disaster response agency, AFAD, had earlier said 17 miners were killed.
Prime Minister Tayyip Erdogan cancelled a day trip to Albania, scheduled for Wednesday, and would instead go to the site of the disaster, sources in his office said.
"Rescue efforts for our brothers in the mine are ongoing ... God willing, in the coming hours, I hope to receive uplifting news," Erdogan said during a speech at a ceremony in the capital Ankara, before the extent of the disaster became clear.
Because the explosion took place during a change in shifts, there was uncertainty over the exact number of miners still inside, but AFAD put the figure at more than 200.
"Fresh air, oxygen is being pumped into the mine. This is the most important thing for our workers down there," Energy Minister Taner Yildiz told reporters, on his way to Manisa.
"We are facing carbon dioxide and carbon monoxide poisoning ... We have to get our friends out of there swiftly."
At least eight people were brought out alive. Television footage showed rescued miners reunited with tearful relatives.
But government officials feared the death toll might be on the rise. "Unfortunately, we could see a grimmer picture. Looks like it will be a very tough night. The death toll may rise but the rescue teams are working hard," one official said.
Turkey's worst mining accident was in 1992, when a gas explosion killed 263 workers in the Black Sea province of Zonguldak. The country has a poor health and safety record in mining, particularly coal.
In May 2010, another gas explosion killed 30 miners, again in Zonguldak province. (Additional reporting by Ece Toksabay in Istanbul and Ozge Ozbilgin and Gulsen Solaker in Ankara; Editing by Nick Tattersall and Eric Walsh)