TOKYO (AP) _ Relatives of people who died in the world's worst single-plane accident today marked the third anniversary of the disaster by visiting the mountain where the jumbo jet crashed.

About 120 relatives and 30 officials of Japan Air Lines, including president Susumu Yamachi, attended a ceremony in heavy rain in Ueno-mura, 80 miles northwest of Tokyo.

On Aug. 12, 1985, a Japan Air Lines Boeing 747 en route to Osaka from Tokyo crashed and killed all but four of 524 people on board. Organizers of victims' family groups said claims for compensation from JAL and the Seattle-based Boeing Co. have been hindered because of the number of people involved in two countries.

''It was the worst airplane accident the world has ever seen, and the aftermath of the accident is highly complicated because the case intertwines interests of more than one country and over thousands of people,'' said Kuniko Miyajima, an organizer of bereaved families.

The Ministry of Transport last year concluded that faulty repair work by Boeing and poor maintenance by JAL after a previous mishap led to the rupture of a rear cabin wall on the aircraft, which caused the crash.

In 1979, the jumbo jet suffered a damaged bulkhead when it skidded on its tail during a rough landing at Osaka International Airport.

So far, families of 334 victims have reached settlement with JAL and Boeing Co., according to JAL officials.

Most families of the remaining victims are either proceeding with suits against JAL and Boeing or individually negotiating with the companies through lawyers, according to Miyajima.

Terms of compensation have not been disclosed either by the companies or lawyers of the families of the victims. However, sources who spoke on condition they not be identified said the cost will be shared by the two companies with 17.5 percent paid by JAL and 82.5 percent by Boeing.

Both JAL and Boeing have admitted liability for the crash and have reportedly offered about $100,000 to $135,000 compensation for each victim, but Miyajima said she is not satisfied with the offer.

''Judging from cruelty of the accident and the pain which bereaved people have to go through, our feeling is that victims deserve at least more than what automobile accident victims get,'' said Miyajima, who lost her 9 year-old son in the crash.

''They have to consider that passengers were exposed to an extreme degree of fear for half an hour while the aircraft was flying in the air without control before crashing,'' she said.

She also said about 30 bereaved relatives of the victims are refusing even to negotiate because ''they cannot get over the pain of facing the agony of losing their beloved ones every time they sit at a negotiation table and discuss the accident.''