Mario Draghi had something new to worry about as he prepared for Thursday's European Central Bank policy meeting: the euro-yen exchange rate.

The yen approached a six-year low versus the shared European currency after Bank of Japan Gov. Haruhiko Kuroda surprised investors late last week by extending his record stimulus program.

Kuroda's actions jeopardize the weaker euro that analysts say Draghi needs to reflate the economy, heaping pressure on him to come up with a policy response.