India cracked down today on growing unrest in the northeast state of Assam, calling out the Army to arrest political leaders and at least 500 picketers who had forced the shutdown of an oil pipeline.

United News of India reported tonight that thousand of persons had been arrested in the Army sweep.

The government action was taken just one week after Prime Minister Indira Gandhi failed to negotiate a solution to a local dispute that has paralyzed the region for seven months. The purpose of the crackdown appeared to be to restore the flow of vitally needed oil from Assam to the rest of the country.

Assam Chief Secretary R. S. Paramashiva said the government instituted a preventive detention order because "secessionist tendencies were developing." a

The indian government has barred foreign correspondents from visiting the unsettled northeast region.

Since October, Assam students have been demonstrating in favor of the expulsion from Assam of all "foreigners" -- including Indians from other states.

The Assamese fear not only that their own culture will be overwhelmed by Moslem refugees from Bangladesh and residents of the neighboring state of Bengal, but also that they will lose political power in their own state to the newcomers. They want as many as 5 million people deported.

The demonstrations were sparked by controversy over who should have been allowed to vote in last January's nationwide parliamentary elections. The unrest caused balloting to be postposed in 12 districts and more than 50 people have been killed since the protests began.

Today's crackdown was the first stern move by the government to contain the unrest that has cut off the flow of oil from an area that account for about one-third of India's total petroleum production.

Army troops moved out early this morning under preventive detention orders promulgated last night. They arrested 14 political leaders in Gauhati and then moved to nearby Narwangi, where the Oil India pipeline carrying crude to a refinery in Bihar had been shut down during 115 days of picketing.

At least 500 perssons were arrested there and police and troops used tear gas and baton charge to halt new demonstrators heading toward the pipeline headquarters. Hospitals reported 100 people were injured.

The government instituted a curfew at 5:30 a.m. but withdrew it seven hours later as 300,000 people took to the streets in defiance of the ban.

P. K. Mahanta, president of the All-Assam Student Union, which has been leading the demonstrations, denounced the government's action and set a 24-hour deadline for India to release those arrested or face more demonstrations.

"The government will not be able to crush a popular movement by force. The arrest of a few leaders and a reign of terror will never dishearten the people of Assam," said Jatin Gaswami, an Assamese political party official.

Leaders of both groups called for civil disobedience, which they said had started by tonight.

Meanwhile, Indian Petroleum Minister Verenda Patil announced in New Delhi that crude oil had started flowing from Assam for the first time since December and that the oil refineries [WORDS ILLEGIBLE], closed for the past four months, should be operating at full capacity by Monday.

Despite the government action, however, United News of India reported tonight that picketing had resumed at the Oil India headquarters in Assam.