NAHA, Okinawa — Okinawans gathered by the hundreds to welcome reversion Monday, and by the thousands to protest the inclusion of U.S. bases in the reversion agreement.

Rain, which caused cancellation of most pre-reversion activities, continued to soak the island Monday, but did little to dampen the enthusiasm of dozens of groups which make up Fukkikyo (Okinawa Reversion Council). More than 5,000 of them turned Naha's Yogi Park into a quagmire, and listened to their leaders protest U.S. military bases on the island and the stationing of Japan Self-Defense Force troops here.

In the Naha Civic Hall, adjacent to the park, 1,300 persons assembled, including the new U.S. Consul General, Richard W. Petree, and Sadanori Yamanaka, director general of the Japanese prime minister's office.

Gov. Chobyo Yara told the crowd that reversion was the consummation of many years of tireless efforts of Okinawans but that it also marked the beginning of a new era of hard work for the island people.

''Reversion day has doubtlessly arrived today ... and Okinawans have become Japanese in name and fact.

"Looking back at those days of hardship, I now share with prefectural people deep, inexpressible emotions," said Yara, who spearheaded the reversion movement in the 1950's and 1960's before he was elected chief executive in 1968.

"But the fact remains that terms of the reversion do not necessarily reflect sincere desires of the prefectural people (in regard to the military bases and many other problems), and many new problems are in store for us," he warned.

He said the primary object for Okinawa in the post reversion era should be an evolution from "the islands of military base" into a "the islands of peace and prosperity" by effective use of human talents, abundant labor and geographical advantages which make Okinawa Japan's "south entrance" to the Southeast Asia.

Referring to 27 years of American rule over the Okinawan people, the governor said it was a valuable experience that had tempered their will and spirit and that it should give them an added impetus and confidence in building a new Okinawa.

Petree told the crowd, "An amicable and mutually agreed reversion of Okinawa to Japanese control has long been an objective of my government and of the government of Japan. Realization of this objective has great significance for the preservation and further strengthening of American-Japanese ties of friendship and cooperation ...

"The people of the prefecture of Okinawa have an important contribution to make to this relationship. The mutual respect, cooperation and understanding existing between Americans and Okinawans in these islands is an asset of great value which the United States will make every effort to maintain and strengthen in the years to come."

At the end of the ceremony, Yamanaka led the crowd in a banzai (long life) cheer.

While the ceremony was going on, about 20 Kakumaru (Revolutionary Marxist) students began warming up for their protest demonstration by trotting back and forth on the veranda of the new Naha Hospital across the street from the civic center chanting, "Crush reversion! Crush the (U.S.-Japan) security treaty! "

Fukkikyo members began pouring into Yogi Park about 3 p.m.

A small group of Americans from an antiwar group called Omega House also took part in the protest rally. One member of the group made a brief speech during the rally denouncing U.S. involvement in Vietnam and the continued stationing of American troops here.

A parade which followed the rally was orderly until marchers reached Kokusai St., Naha's main street. There, demonstrators and some bystanders began ripping down banners, signs and Japanese flags with which merchants had decorated the street. Some 400 riot police stood by until the parade neared the Naha Police Headquarters.

A group of about 30 Han-Sen (antiwar) faction students menaced police guarding the headquarters with bamboo flagpoles.

A police spokesman said Tuesday that four students were arrested during the brief melee in front of police headquarters and have been charged with vandalism.

Police jerked flagpoles from the students and tossed them into the gutter along with large photographs the protesters had carried of Vietnam war and atomic bomb victims. The students fled to the Okinawa Prefectural Government Plaza a block away, then moved back toward the police headquarters three times shouting abuse and shaking their fists at police. They were finally dispersed about 8 p.m.

Earlier in the day, Yara — who will serve as interim governor until gubernatorial elections are held in June — unveiled a plaque on the former Government of the Ryukyu Islands capitol, designating the building the new prefectural capitol.