Japan says Russian planes intruded into Japanese airspace for over 1 minute on February 7, 2013, over the island of Rishiri, near Hokkaido. F-2 aircraft from Japan's Self Defense Forces responded to the intrusion. The intrusion comes at the time of the Northern Territories Day when Japan's government reiterates its determination to press for return of the Northern Territories from Russia. Japan did not sign a peace agreement with Russia at the end of World War II after Russia refused to leave the islands. The islands are known as the four Kuril islands in Russia. Policy experts at Japan's National Graduate Institute for Policy Studies say the Russian intrusion was an attempt to test Japan after an incident where Chinese radar locked in on Japanese naval ships in the East China Sea. The effects on public opinion are likely to create support for prime minister Abe's effort to increase the budget for Japan's Self-Defense Forces.