Dropping leaflets is the latest Rhodesian tactic in an escalating war against black nationalist guerrillas-even within the countries that shelter them - to prevent disruption of elections later this month for Salisbury's first black-led government.

The Rhodesian counteroffensive has spread to three independent black countries helping the guerrillas. It has included heavy bombing of guerrilla bases, depots and supply lines all across Mozambique, stepped up infiltration of antiguerrilla commando groups into that country as well as Zambia, a daring air attack on a nationalist camp in eastern Angola and increased assistance to dissidents fighting to overthrow the Mozambican government.

The dissidents were responsible for a recent fire at an oil depot outside Beira in central Mozambique resulting in $16 million in damage, apparently Rhodesian retaliation for a guerrilla attack Dec. 12 on Salisbury's main oil storage center in which 22 tanks worth more than $18 million were destroyed.

Last weekend, a Rhodesian military plane trying out a new tactic dropped leaflets on a southern Zambian town exhorting war-weary Zambians to turn against the guerrillas based in their country.

The Rhodesian bid to undermine Zambian support for the guerrillas apparently is timed to take full advantage of growing strains between Zambia and the zimbabwe African People's Union (ZAPU), which is led by Joshua Nkomo and headquartered here in Lusaka.

Misbehavior by some Nkomo guerrillas has alienated an increasingly large segment of the Zambian population and at least part of the government, although Zambian President Kenneth Kaunda shows no signs of wavering in his support.

Since Rhodesia began bombing Nkomo camps in Zambia last October, more and more guerrillas have begun attacking Zambians and expatriate white farmers, particularly around the Capital and Livingstone, near Victoria Falls on the Zambian-Rhodesian border.

The worst incidents occurred in early January when guerrillas ambushed and killed an Asian woman and a Zambian farmer driving along a main highway and in February when a white Zambian mechanic was shot to death outside the capital and a white expatriate farmer outside Livingstone was badly hurt.

At first the Zambian press blamed these attacks on black Rhodesian commandos belonging to the hated Selous Scouts, an outfit equivalent to the American Green Berets.

The mechanic's killing, however, sparked the first public outery against Nkomo in the local party-controlled newspaper, The Times of Zambia, which warned of a possible crackdown on guerrilla activites.

"There is no excuse and no justification for bands of armed men from a foreign country creating a reign of terror in Zambia," The Times said in an editorial Feb. 21. It called for "rigid control" of the guerrillas to avoid a confrontation.

The Rhodesian leaflets dropped over the weekend on Mazabuka, a farming community 50 miles southwest of Lusaka and 30 miles from the Rhodesian border, played heavily on this antagonism toward the guerrillas.

"Citizens of Zambia," they said, "the people of Zambabwe-Rhodesia have no quarrel with the people of Zambia. Our security forces' attacks are aimed at Nkomo's bandits operating inside Zambia. Why does your government continue to support Nkomo's men and force us to attack them inside Zambia?

"Nkomo's men eat food that should go to Zambians and they shoot down Zambian airplanes. They outnumber the Zambian Army and are a threat to all Zambians."

The mention of Zambian aircraft shot down referred to another February incident in which guerrillas reportedly fired missiles at two Zambian Air Force jet fighters flying over their camps near Lusaka and destroyed both.

Last Friday, guerrillas derailed a train inside Rhodesia filled with Zambian copper heading for South African ports. The Rhodesians, possibly as part of their psychological warfare here, gave prominent coverage to the derailment.

The result of Rhodesia's military and propaganda offensive here and in Mozambique is difficult to determine. About 1,000 Rhodesian blacks were killed or wounded in the first series of raids on Nkomo camps in October and November. But not many were battle-ready guerrillas.

Probably the single most punishing raid came in Angola on Feb. 26 when Rhodesian bombers flew across Zambia to hit a training center there. Angolan authorities said 192 persons were killed and nearly 1,000 others injured. Nkomo officials here privately concede it was a serious blow, although they stress there is no shortage of guerrilla recruits.

Leaders of the Mozambique-based Zimbabwe African Nation Union (ZANU), the larger of the two guerrilla armies, say their forces are almost entirely inside Rhodesia and that the raids are inflicting more damage on the Mozambican economy than on them.

The real measure of Rhodesian or guerrilla success will come during the elections, when the war now claiming 1,000 casualties a month is expected to become even bloodier. CAPTION: Map, no caption, By Richard Furno-The Washington Post