MOSCOW (AP) _ Strikers at the largest coal mine in the Vorkuta region of the Soviet Arctic agreed Friday to go back to work after wresting a promise of independence from outside authorities, Tass reported.

The decision to return to work ends a five-week-long strike across 13 mines in the northern region. The strikers were demanding the government make good on pledges it offered to end a nationwide coal strike last summer.

The workers at the Vorgashorskaya mine were the last still on strike. They will return to work Saturday, the official Tass news agency said.

They made the decision after a copy of new regulations granting them independence from regional authority was approved by the Coal Minister Mikhail Shchadov and sent to the Vorkuta mine, Tass said.

Tass said the new rules grant the mine ''full independence.'' It said the mine can even ''terminate its subordination'' to the official coal association, provided it keeps fulfilling state orders for delivery of coal to consumers.

Miners began the walkout at the 13 shafts around Vorkuta, 950 miles northeast of Moscow, on Oct. 25 to press demands that the government fulfill promised increases in pensions and wage differentials for hazardous working conditions. They also sought pledged improvements in living conditions.

The government made the promises to end strikes that gripped nearly all the country's coal fields in July.

Miners' representatives met in the Kremlin with Premier Nikolai I. Ryzhkov on Nov. 17 to discuss their grievances. Ryzhkov was reported to have said pension increases and longer vacations were provided for in legislation making its way through the Soviet legislature.

Tass said coal supplies were still down, even though other mines had begun operating normally. It gave no figures.

12EST