Rebels seeking to overthrow Mozambique's Marxist government have introduced a new element of cold war politics into the conflict with their bold killing of two Soviet mining technicians and kidnaping of two dozen others this week.

The Soviet Embassy in Maputo confirmed today that the South African-backed Mozambique National Resistance movement overcame government militia forces in a dawn raid Sunday on the Morrua mine in Mozambique's populous Zambezia Province, killing and capturing the Soviet technicians. The Mozambican Defense Ministry, also announcing the deaths in a communique, added that two Mozambican workers, members of the militia guarding the mining site, were killed in the attack, and four Mozambicans were kidnaped with the Soviets.

A diplomatic source in Maputo interviewed by telephone called the raid "a very surreptitious attack" that seemed to single out Soviets deliberately. The operation appeared unusually well planned, sources said, leading to speculation that South African strategists, who have sought to draw attention to the Soviet presence in Mozambique, were involved at least in the planning.

There are several thousand western and Soviet Bloc specialists and technicians attempting to aid Mozambique's development programs. Mozambique, according to the World Bank, ranks as one of the world's 20 poorest countries. There are also approximately 800 to 1,000 Soviet, East German and Cuban military and security advisers.

There have been no indications that the 24 Soviet captives had any military role. The resistance movement had taken hostage more than 50 foreigners during the past three years, but Sunday's raid marks the first time that the rebels have singled out Soviet advisers. In the past, most hostages have been released unharmed, some after as long as eight months' captivity, although six Portuguese have been killed and six Bulgarian captives reportedly were freed last November by Mozambican troops.

The MNR, which has about 10,000 guerrillas, has been engaged in sporadic military attacks and economic sabotage for the past six years. Many observers believe South Africa has used the movement as a tool to bleed Mozambique economically and keep the Marxist government unstable. South African officials have denied seeking to destabilize Mozambique but have not denied offering some assistance to the rebel group.

The raid on the Morrua mine, which netted the largest number of hostages yet taken by the group, was a clear embarrassment to the government of President Samora Machel. Only tonight--four days after the attack--did the government officially acknowledge the raid, which was revealed by a Tass correspondent in Maputo yesterday.

Just two weeks ago, Machel had announced plans to launch a major new military offensive against the rebels in Zambezia Province.

Zambezia, with a population of 3 million, is Mozambique's most populous province. A mining and agricultural center, it produces nearly half of the foreign exchange the country earns through exports.

The French news service Agence France-Presse reported from Maputo that the Morrua site was being developed to produce tantalite, a metallic ore used in the production of nuclear reactors, aircraft and missile parts. Zambezia has extensive deposits of tantalite, AFP reported.

The Mozambican Army reportedly achieved some successes earlier this year in driving rebel forces out of central Manica and Sofala provinces. Those forces appear to have regrouped to the south in Inhambane and to the north in Zambezia, sources said. Besides being the hub of Mozambique's limited wealth, Zambezia shares a long and unpatrolled border with Malawi, from which many of the rebels are said to operate.

Sources in Maputo said today that there are reports of regular supply flights by MNR small planes from Malawi into Zambezia despite a pledge earlier this year by the Malawian government that it would do what it could to deny access to the rebels.