Two white women missionaries were shot dead by black nationalist guerrillas who attacked a Roman catholic mission in southwestern Rhodesia, a Rhodesian government spokesman said yesterday.

The attack took place amid increasing diplomatic activity in advance of a meeting in London Friday on the future of Rhodesia. It coincided with reports from Botswana that Rhodesian troops attacked Botswana forces this morning.

The two women were killed Tuesday at St. Paul's mission, about 220 miles southwest of Salisbury, the Rhodesian capital.

They were identified as Johanna Decker, 59, a German-born physician [WORD ILLEGIBLE] Munich; and Sister Ferdinanda, an Austrian nun who recently voluntered for mission work in Rhodesia. [WORD ILLEGIBLE] Decker had worked in the Rhodesian bush country for more than 20 years.

One nursing sister, the only white at the remote mission to survive, said the guerrillas punched and assaulted black nurses, threatening them with rape, and forced patients from the beds.

The guerrillas said to belong to nationalist forces fighting for black-majority rule in Rhodesia, demanded money from the missionaries. The two victims were shot in the back, according to the white nursing sister who said she survived by hiding.

Meanwhile, Rhodesian nationalist leader Bishop Abel Muzorewa arrived in London yesterday for talks with British Foreign Secretary David Owen and said he would demand an acceleration of the process toward majority rule in Rhodesia.

Muzorewa said he expected the talks to be "tough and very rough" but added: "We have made up our minds that we are not going to sit down and watch people play politics."

Also arriving in London Thursday is South African Foreign Minister R.F. (Pik) Botha, who will attend a meeting Friday with Owen and Secretary of State Cyrus Vance. British sources in London were quoted as saying that Vance and Owen would complete Friday revised Anglo-American proposals for bringing the breakaway British colony to black-majority rule by the end of next year and present them to Botha.

Muzorewa's arrival preceds that of Tanzania's President Julius Nyerere, who is scheduled to hold talks with British Prime Minister James Callaghen Saturday on prospects for the new Anglo-American initiative on solving the Rhodesian problem. Nyerere had just completed talks on the subject with President Carter in Washington.

One of Muzorewa's rivals for power, Joshua Nkomo, who is currently touring Caribbean countries to round up support, met late Tuesday night with U.S. Ambassador to the United Nations Andrew Young at Georgetown, Guyana. The American envoy, who is also visiting several Caribbean nations, said today that in many respects Nkomo seemed much more moderate than he had been led to believe.

Young said he was gratified to learn that Nkomo wants eventually reconciliation between the racial and political sides in Rhodesia, and that he wants whites to stay on, despite Nkomo's continued dedication to armed struggle as the only way to get majority rule.

"I think that he's always been very concilatory," Young said. "What happens to him, I guess, is that he still believes that Zimbabwe's independence depends on continued armed struggle and that's the only part that gets reported."