KHOBAR, Saudi Arabia, Nov 24 (Reuters) - Saudi Electricity Co (SEC) signed two contracts worth around 1.7 billion Saudi riyals ($453 million) with U.S. General Electric for maintenance of gas turbines at new power plants in Riyadh, SEC said on Sunday.

The deal, which would run for 25 years split between 8 basic years and 17 optional years, would cover maintenance work on the 12 gas units for the combined-cycle power plants, SEC said.

This follows a previous deal signed on Wednesday in which GE will supply SEC with 12 gas units and four steam turbines for the planned Riyadh Power Plant 13 (PP13) and PP14.

Each plant would have a capacity of between 1,600 and 1,950 megawatts, an industry source has said.