TOKYO (AP) _ Earthquakes rocked southwestern Japan for the fourth straight day on Monday, stirring up fears that a major earthquake might be imminent.

More than 5,700 quakes have been registered since Friday, 95 of which were strong enough to be felt, according to the Central Meteorological Agency.

The strongest quake, Sunday, registered a 4.8 magnitude, but there were no reports of injuries or significant damage.

Television footage Monday showed fallen tombstones, porcelain goods toppled from shelves and cracks in walls. A train line was halted for about 90 minutes Sunday to check track safety.

Yoshiaki Ida, chairman of the Coordinating Committee for the Prediction of Volcanic Eruptions, an meteorological advisory panel, said a relatively large earthquake may occur. She could not predict when.

Top government spokesman Koken Nosaka told journalists on Monday that the government was ``gravely concerned'' about the quakes, centered near the Ito hot springs resort 60 miles southwest of Tokyo.

The temblors have caused jitters among tourists who fear a larger quake could be in the offing, and some guests canceled reservations at the spa, officials said. Some residents in the quake area also expressed fears of a bigger earthquake, news reports said.

A series of quakes in the area have been reported every year for the last decade, and the meteorological agency is checking for volcanic activity, a government seismologist said. There are more than 100 undersea volcanoes off the coast of eastern Japan.

Japan is one of the world's most seismically active countries, accounting for about 10 percent of the world's earthquakes and volcanic activity each year.