Japan rocketed two spy satellites into space from this remote island Friday, giving it orbiting eyes to monitor North Korea's missile and suspected nuclear weapons programs.

North Korea has called the launch as a "hostile act," warning it might test-fire a missile in response.

The satellites, the first of at least four in the $2.05 billion spy program, were launched into clear but windy skies atop an H2-A rocket, the centerpiece launch vehicle of Japan's space program.

"The rocket has successfully lifted off," flight controllers announced minutes afterward. "It is flying smoothly and is on course."

The satellites will allow Japan to monitor neighboring North Korea's suspected development of nuclear weapons and to provide advance warning of long-range missile tests. But officials maintain they're not intended as a provocation and will be used for other missions, such as monitoring natural disasters.

But they admit the program was prompted by the 1998 "Taepodong shock," when a North Korean Taepodong ballistic missile flew over Japan's main island before crashing into the Pacific off Alaska in 1998.

North Korea, however, has protested that the spy program as a "grave threat" that violates the spirit of a bilateral agreement reached six months ago that included a moratorium on long-range missile launches. There was no immediate reaction early Friday from North Korea.

The launch from the Tanegashima Space Center, a sprawling complex of launch pads on this rugged island about 700 miles southwest of Tokyo, marked a milestone for Japan's space program, which had previously been limited to strictly nonmilitary, peaceful missions.

The two satellites, which have both conventional photographic and radar imaging capabilities, are expected to be in use for about five years. If all goes well, they will orbit 250-370 miles over earth and be able to supply images regardless of weather conditions below.

The date for the subsequent launches has not been announced.

The paucity of clear data on what Japan's enigmatic communist neighbor is doing is one reason why Tokyo wants its own eyes in orbit.

Japan now gets its intelligence primarily from the United States, which, along with spy satellites of its own, conducts frequent surveillance flights out of an air base on the southern Japan island of Okinawa.

But heightening tensions over the North's suspected development of nuclear weapons and its increasingly hostile stance toward Washington have caused deep concern in this country -- virtually all of which is within range of its Taepodong missiles.

To discourage any brinkmanship, the United States, which has roughly 50,000 troops stationed in Japan, has deployed one of its aircraft carriers off the Korean Peninsula and bombers to the Pacific island of Guam.

Tokyo also sent an Aegis-equipped destroyer to the Japan Sea, which lies between Japan and North Korea.

But with Washington's attention focused on its war on Iraq, Pyongyang has shown little interest in easing regional fears.

A North Korean government spokesman, quoted in the North's official media last week, hinted that if Tokyo went ahead with the launch Pyongyang might test-fire a long-range missile of its own.

U.S. and Japanese officials say the North could be preparing such a test, but add there is no conclusive evidence a test is imminent.

North Korea recently launched a short-range missile on the eve of the inauguration of South Korea's president and significantly escalated tensions by sending its fighters to intercept one of the Japan-based American spy flights while it was in international airspace.

No shots were fired, and the plane returned safely to Okinawa. Washington strongly protested the incident, but has since resumed the flights.