Bank of Japan Gov. Masaaki Shirakawa said on Saturday policy makers are closely watching the impact of looser monetary policy on crude-oil prices.

Along with the European Central Bank and the U.S. Federal Reserve, the Bank of Japan is taking unconventional steps to boost the economy. For examples, it boosted asset purchases by 10 trillion yen on Feb. 14, and it pledged to keep ultraeasy policy until a 1 percent inflation goal is in sight.

Speaking at a Group of 20 meeting in Mexico City, Shirakawa said policy makers were closely watching the effects -- and side effects -- of monetary easing on crude prices, which rose above $125 a barrel to end in proximity to a 10-month high on Friday.

But Shirakawa said he did not see monetary easing as a big factor and that the recent spike was more likely due to geopolitical tensions, meaning Brent oil's recent gains have been fueled mainly by worries over Iranian supply.

Behind the United States and China, Japan ranks No. 3 among countries in terms of total crude-oil consumption.

(Reporting by Tetsushi Kajimoto; Writing by Krista Hughes)