CSN will raise Brazil steel prices by 7.5 pct

* CSN seeks raise to counter surge in iron ore

* Will adopt a quarterly pricing system

* Shares fell in Sao Paulo on Wednesday

SAO PAULO, April 14 (Reuters) - CSN, Brazil's second largest producer of flat steel, will raise domestic prices by as much as 7.5 percent in the second quarter to counter a recent doubling of the cost of iron ore on international markets, Chief Executive Benjamin Steinbruch said on Wednesday.

The Sao Paulo-based steelmaker, also Brazil's largest diversified steelmaking group, will adopt a quarterly pricing system to mimic pricing movements in global ore markets, Steinbruch told reporters at an industry event.

"We are too far away from recouping some of the discounts that we all awarded last year," he said. "What we are doing now is basically catching up with the iron ore companies."

The action comes as Brazil's Vale (VALE5.SA), the world's largest producer of iron ore, and rivals including BHP Billiton will price the metal quarterly from April 1. A new round of price increases by rival steel companies is likely as supply of the metal remains tight and the cost of coal rises globally.

Analysts have said steel companies are more likely to charge higher prices for distributors first. Some specialized clients will only be told of price increases in the second half of the year.

Shares of CSN (CSNA3.SA)(SID.N) fell 0.3 percent to 35.70 reais. Shares have more than doubled over the past 12 months. (Reporting by Alberto Alerigi Jr; Writing by Guillermo Parra-Bernal)