The discovery of nearly 200 decomposed bodies left in the wake of a previously unreported massacre in the riot-torn Indian state of Assam has pushed the unofficial death toll in the violence there to at least 2,500 and has given rise to fears of more unreported carnage in remote areas.

Indian reporters in the Darrang district of Assam, along the Brahmaputra River, today said more than 500 persons were believed killed in a massacre in the remote villages of Chalkhowa Chapori and Dholpur on Feb. 22, but that police search parties did not reach the scene until Thursday because bridges and access roads had been cut.

Foreign journalists for years have been banned from Assam, which India considers a strategically sensitive border region.

The newly reported massacre appears to be the worst since the Feb. 18 Hindu tribal attacks in the area of Nellie, in which an estimated 1,000 Bengali-speaking Moslem immigrants from what is now Bangladesh were reported killed.

Reports from Darrang were still sketchy today because of the remoteness of the villages, and Indian Home Affairs Ministry officials refused to comment on the reports.

But Indian news agency reports from the Assamese capital of Gauhati said thousands of indigenous Assamese attacked a cluster of villages, burned houses and, using spears and machetes, hacked to death Bengali Moslems and Hindus and even some Bengali-speaking Assamese Hindus in what appeared to be language-motivated violence.

The communal riots, which began in mid-February, were sparked by the government's insistence on holding state elections in defiance of demands by militant Assamese that Moslem immigrants first be striken from the electoral rolls and some deported.

The official death toll stands at 1,625, but unofficial estimates have run as high as 3,000. The overall figure may never be known because thousands of villagers have fled Assam and many victims are believed to have been buried in dense forests or thrown into rivers.

Home Affairs Minister P.C. Sethi said last week that 230,000 people in Assam had been left homeless, including many who fled to neighboring West Bengal state.

The Home Affairs Ministry, responding to a journalist's request for a travel permit to Jalpaiguri in West Bengal, where 35,000 refugees are settled in camps, said that the northern part of West Bengal had been declared a closed area and that the request had been forwarded to the Foreign Ministry and the Intelligence Bureau for "study." A ministry official said the decision was made because of the rioting in Assam.

Indian journalists have been allowed to travel to Assam, but Prime Minister Indira Gandhi has said that the presence of foreigners in the troubled state would be provocative.