Three home-made rockets were fired at the U.S. Consulate in Kobe early today but they caused no injuries or damage, Kobe police reported. A leftist extremist group said it had fired the rockets to protest Prime Minister Yasuhiro Nakasone's visit to the United States.

Three Japanese security guards were on duty inside the two-floor building when the rockets, about two-feet long and made of wood, were fired from a park about 100 yards away just before 6 a.m.

One soared over the building and exploded. The other two landed inside the consulate's grounds but only one exploded. Police later found a wooden launching device equipped with a primitive timer in the park.

Several hours later, Japanese media received telephone calls from people identifying themselves as members of the Middle Core Faction Revolutionary Army, an underground radical group.

The rockets were meant to protest the scheduled Reagan-Nakasone meeting between, the callers said. Nakasone left Japan today as about 1,200 leftists demonstrated outside Haneda Airport.

Nakasone later arrived in Los Angeles where he will meet Reagan Wednesday. The talks are expected to dwell on growing U.S. concern over the large U.S. trade deficit with Japan, Reuter reported .

The Middle Core group has long been connected with a battle to stop construction and operation of Narita Airport outside the capital. Three months ago, it claimed responsibility for a firebomb attack that gutted the interior of the headquarters building of Nakasone's Liberal Democratic Party.