With the help of three black opposition legislators and two whites summoned from sickbeds, Rhodesian Prime Minister Ian Smith today narrowly won approval in Parliament for a controversial bill that will allow blacks to buy land previously reserved for whites.

The bill passed the 66-member house with exactly the two-thirds majority it required, 44 to 22.The victory gave Smith's government the "vital element" it requested in its bid to achieve an "internal" majority rule settlement.

Smith's intention has been to promote an internal settlement rather than one reached through international intervention. His plan is to win support from local blacks, whom he considers less radical than the internationally known leaders of the black nationalist movements.

The bill reduces areas reserved for ownership by Rhodesia's 270,000 whites from 50 per cent of the country to less than 1 per cent.The 6 million blacks will be able to buy land in most of the country but will remain barred from white residential areas and white schools and hospitals.

Twelve members of Smith's white Rhodesian Front refused to support the bill. Three of 13 opposition black legislators supported the bill and two Smith supporters who are recovering from recent heart attacks were brought to Parliament to vote, one in a wheel chair.

David Martin of the London Observer reported from Lusaka, Zambia:

Rhodesian Roman Catholic Bishop Donal Lamont has expressed doubts as to whether 12 Catholic missionaries killed in Rhodesia recently were slain by guerrillas, as Smith claims, or by government security forces masquerading as guerrillas.

Lamont, who has been sentenced to a year in prison for failing to report the presence of guerrillas at church facilities in his diocese of Umtali on the Mozambique border, made his comments in an interview.

He illustrated his doubts by recounting this incident:

"I had a visit from one of my African clergy who reported he was terrorized by European [white] memebers of the security forces and they said to him: "You'd better watch out. One dead missionary is as good as a hundred dead terrorists to us.'"

These may have only been words, Lamont said, but they were a "horrible" reflection of the state of Rhodesian society.

Fifteen months ago in Salisbury, a former senior member of the Rhodesian army told me categorically that members of the security forces were killing civilians and making it appear that the guerrillas were responsible.

Lamont's doubts and the former officer's assertions do not prove that the missionaries were killed by government forces, but they bring into question Smith's claim that guerrillas were responsible.