By Uditha Jayasinghe

COLOMBO, March 22 (Reuters) - Sri Lanka ordered its military to post soldiers at hundreds of gas stations on Tuesday, to help distribute fuel after a sudden rise in prices of key commodities and the accompanying shortages forced tens of thousands of people to queue for hours.

The Indian Ocean island nation is battling a foreign exchange crisis that forced the devaluation of its currency and hit payments for essential imports such as food, medicine and fuel, prompting the government to approach the IMF.

The decision to position troops near petrol pumps and kerosene supply points came after three elderly people dropped dead during their wait in long queues, officials said.

"At least two army personnel will be deployed at every fuel pump," military spokesman Nilantha Premaratne told Reuters, adding that the soldiers would help organise fuel distribution, but would not be involved in crowd control.

The move was a response to complaints of stockpiling and inefficient distribution, said government spokesman Ramesh Pathirana.

"The military has been deployed to help the public, not to curtail their human rights," he added.

Tension over scarcity of supplies has led to sporadic violence among residents jostling to buy fuel and other essential items.

Police said a man was stabbed to death on Monday in an argument with the driver of a three-wheeled vehicle, while last week three elderly men died while queuing to buy fuel in sweltering heat. (Reporting by Uditha Jayasinghe; Editing by Rupam Jain and Clarence Fernandez)