TOKYO — Workers were pumping more than 3 million gallons of contaminated water from Japan’s tsunami-ravaged nuclear power complex into the Pacific Ocean today, freeing storage space for even more highly radioactive water that has hampered efforts to stabilize the plant’s reactors.

The government also has asked Russia for a ship that is used to dispose of liquid nuclear waste as it tries to decontaminate the Fukushima Dai-ichi nuclear complex, whose cooling systems were knocked out by the magnitude-9.0 earthquake and tsunami on March 11.