Rhodesia made its deepest and most dramatic strike into neighboring Zambia yesterday, sending its aircraft 80 miles across the border to bomb what it described as a black nationalist guerrilla camp just 12 miles north of the capital, Lusaka.

The Rhodesian military said the planes had attacked "the main controlling military headquarters" for operations of the Zimbabwe African People's Union (ZAPU) led by Joshua Nkomo.

Both the Zambian government and Nkomo described the site at Chikumbi as a refugee camp only, however. The first government reports said dozens were killed and more than 300 wounded, but unofficial and unconfirmed estimates put the number killed at as many as 300.

Reporters saw dozens of wounded young men being brought by car and Land Rover to the main hospital here.

A second Zambian government communique late last night said four jets and American-made Chinook helicopters were involved. Some witnesses said they had seen three helicopters and four jet fighters.

The attack on Chikumbi came on the eye of talks in Washington between U.S. officials and the four leaders of Rhodesia's biracial transitional government. The four are visiting the United States to drum up support for the interim government set up by the so-called "internal" settlement of last March.

The Carter administration hopes to persuade Rhodesian Prime Minister Ian Smith and his three black colleagues to attend peace conference with the nationalist guerrilla leaders. Smith has said since his arrival in the United States that the four are now ready to go to such an all-parties conference but only if there are no preconditions for negotiations.

In addition to striking into Zambia, Rhodesian forces carried out the second series of attacks in the last month against guerrilla bases in Mozambique yesterday. They struck from both air and ground.

Unlike Marxist Mozambique, which has been the target of frequent Rhodesian raids, Zambia, which has good relations with the West, has been left relatively untouched despite the presence of thousands of guerrillas fighting the white-dominated Smith government. In interviews in Washington Smith has said that "his friends," whom he defined as South Africa and the United States, had warned him not to raid Zambia.

[In Washington, the State Department issued a statement saying it deplored yesterday's raids as "a serious extension of the Rhodesian conflict."]

There was speculation here that the simultaneous raids, the first such major dual operation in the six-year-old war, may have been mounted partly as a show of Rhodesian military strength to impress the Carter administration.

However, the raids also were consistent with Smith's recent warning that Rhodesian forces intended to hit hard at rear camps in neighboring countries.

[In Washington, Smith and one of his black colleagues, Bishop Abel Muzorewa, defended the raids, saying they were necessary to protect Rhodesia against terrorism.]

[Smith, speaking to a luncheon audience, said he had received his first information about the Zambia raid only a few minutes earlier.]

"Our forces work from a charter to defend the national security," he said. "They don't have to come to us for permission."

(Muzorewa said, "Advance word is unnecessary. The army is given this freedom of action in defending the country."

[Smith said the terrorists are "massarcing an average of 30 people a day, most of them blacks." He went on: "What are we supposed to do? Sit down and take this? . . . My guess is that there will be another raid today in Mozambique. Maybe another in Zambia tomorrow. I hope we go on having bigger and better raids every day until the terrorism ends."]

Chikumbi is about 80 air miles inside Zambia from the nearest Rhodesian air base at Kariba. It was not known here whether the Rhodesian planes had flown from the airport there or another closer to Salisbury.

The Rhodesian communique gave no details of the Chikumbi raid but witnesses said at least four planes took part.

In an interview later, ZAPU president Nkomo said two British-built Hawker Hunter fighters and three French-made Mirages had taken part and had dropped unusally heavy bombs.

He said the Rhodesians do not make such bombs and suggested that they might have come from the United States.

While the Rhodesians are known to have Hawker Hunter aircraft, no independent diplomatic or journalistic source has been able to confirm the guerrillas' belief that they have obtained Mirages from South Africa. The attack on Chikumbi lasted less than five minutes. At least 10 explosions were heard in Lusaka, where windows rattled and houses shook.

The main blasts were followed by smaller ones, suggesting that the bombs may have set off secondary explosions. Black smoke rose from the site for hours afterward.

Reporters traveling into the vicinity of the camp saw ZAPU guerrillas with new Soviet-made AK47 rifles standing along the main road and several truckloads of guerrillas racing from the capital toward the scene of the bombings. The camp was closed to reporters.

Whether Chikumbi was ZAPU military headquarters or a camp for refugees only, was difficult to establish.

All of the wounded delivered to the main hospital here were young men, but most were not wearing military uniforms. Nkomo said the camp contained recruits who had been rejected for guerrilla service and included some sick and blind people.

The camp did not appear to be heavily defended, according to two Western correspondents who got as far as the main gate.

There was some speculation here that the Rhodesians may have targeted a site just outside the capital in an effort to weaken Zambia's resolve to continue supporting the guerrilla cause.

If nothing else, the attack demonstrated that the Rhodesians can strike the Zambian capital area without being shot down by Zambian defense forces.

The attack may raise again the question of whether Zambia should call in outside forces to bolster its defenses. President Kenneth Kaunda has repeatedly hinted that he might turn to Cuba, but so far he has directed his requests for military aid to Britain and the United States.

Britain is reported to have agreed to send military technicians to help repair Zambia's largely nonfunctioning Rapier ground-to-air missile defense network, but it has denied London press reports that it is preparing to send a battalion of troops to protect Zambia against Rhodesian attacks and to bolster the Kaunda government generally.

Kaunda is under considerable pressure to change his policy toward Rhodesia. The country's economic situation reached crisis proportions with 90,000 tons of vitally needed fertilizers stranded in Mozambique and shortages of key commodities like rice, flour and butter persisting.

Meanwhile, Kaunda faces general parliamentary and presidential elections, Dec. 12.

Kaunda announced Oct. 6 the partial reopening of the Rhodesian border, closed nearly six years ago to tighten the U.N. imposed economic blockade against the white minority Rhodesian government. The measure was taken to allow thousands of tons of undelivered Zambian imports and exports to be shipped via the southern rail route through Rhodesia to and from South African ports.

But Kaunda's main political opponents have been demanding that Zambia open its entire border with Rhodesia, resume trading, and in effect normalize its relations with the Rhodesian government. This the Zambian leader has refused to do.