TOKYO: Japan launched two intelligence satellites into orbit on Sunday amid growing concerns that North Korea is planning to test more rockets of its own and possibly conduct a nuclear test.

Officials say the launch Sunday of the domestically produced HII-A rocket went smoothly and the satellites - an operational radar satellite and an experimental optical probe - appear to have reached orbit.

Japan began its intelligence satellite program after North Korea fired a long-range missile over Japan's main island in 1998. North Korea conducted a launch last month that it says carried a satellite into orbit but has been condemned by the U.S. and others as a cover for its development of missile technology.

The latest Japanese launch was in the planning stages long before the current increase in tensions with North Korea, but underscores Japan's longstanding wariness of its isolated neighbor's abilities and intentions.

The radar satellite, which can provide intelligence through cloud cover and at night, is intended to augment a network of several probes that Japan already has in orbit. The optical probe will be used to test future technology and improvements that would allow Japan to strengthen its surveillance capabilities.

Japan still relies on the United States for much of its intelligence.

Its optical satellites are believed to be about as good as commercial satellites, meaning they are able to detect objects of about 40 centimeters (16 inches) in size from their orbits. With the additional radar satellite, Japan hopes to be able to glean intelligence on any specified location once a day.

Japan, which hosts about 50,000 U.S. troops, is especially concerned about North Korea because its main islands are already within range of the North's missiles. Along with developing its own network of spy satellites, Japan has cooperated with Washington in establishing an elaborate missile defense shield.

North Korea's powerful National Defense Commission declared last week that the country would carry out a nuclear test and launch more rockets in defiance of the U.N. Security Council's announcement that it would punish Pyongyang for its long-range rocket test in December with more sanctions, calling it a violation of a ban on nuclear and missile activity.

North Korea's state news agency said on Sunday that leader Kim Jong Un vowed at a meeting of top security and foreign officials to take "substantial and high-profile important state measures."