Rhodesia's seven-year-old guerilla war, black africa's bloodiest struggle for independence, came to an official end at one minute before midnight last night with the imposition of a nervously observed fragile truce.

Commonwealth troops, charged with monitoring the cease-fire, reported half an hour after the truce went into effect that some Patriotic Front guerillas turned up at four points where they are to gather over the next week. No numbers were given, but a British spokesman said it was "certainly not in the hundreds."

The initial contact with the guerillas "was encouraging," the official said, but he cautioned that it was far too early to judge the success of the cease-fire, which calls for the guerillas to assemble at 16 sites by next Friday.

So far, there have been no reports of fighting, he said, adding that 36 of the 40 monitoring teams have been deployed without incident. The other four teams have been delayed by bad weather, the official said.

The lightly armed Commonwealth troops are not allowed to prepare any defenses around the camps where the guerillas are to gather and keep their weapons. The monitoring force is only allowed to fire in self-defense.

The officials said Rhodesian security forces had disengaged and returned to 40 base areas as required, leaving law and order in the hands of the police.

The war, which has killed at least 10,000 went on apace right up to the last official day of fighting. The Rhodesian military announced that 31 persons, including four members of the security forces, were killed Thursday.

In Salisbury, the activation of the cease-fire passed unnoticed, just like other events of the last two weeks that have begun the process of major change to bring Rhodesia from an unrecognized, white-controlled government to legal, black-majority status.

Salisbury has treated with nonchalance the dissolution of Bishop Abel Muzorewa's government, the official end to the unilateral declaration of independence proclaimed by former prime minister Ian Smith 14 years ago, and the arrival of Britian's governor, Lord Soames, who will run the colony until a new government is elected.

Frustrated by the bloody war that has killed at least 20,000, most Rhodesians seem to be waiting to see if the cease-fire really works.

Implementation of the cease-fire coincided with an announcement by Soames that elections for a black-majority government would be held in two months under provisions of a settlement reached in London last week.

Soames set Feb. 27, 28 and 29 as the dates for Africans to elect the 80 members of the 100-seat black-majority Parliament Representatives of the 220,000 white minority will be elected Feb. 14, he said.

The British are scheduled to end their brief return to colonialism in Africa after the formation of a new government based on the results of the election.

Britain has taken on the responsbility of ensuring that the elections are free and fair. One key element in determining this will be whether the cease-fire is effective and allows political campaigning to be carried out

The British have drawn up intricate plans for implementing the truce involving the use of 1,300 cease-fire monitoring troops from the Commonwealth, an organization of Britain and its former colonies. More than 1,000 of the troops are British with Australia, New Zealand, Kenya and Fiji providing token forces.

The troops are to monitor the activities of both the Patriotic Front and the Rhodesian security forces, which pulled back to the vicinity of their bases yesterday.

The 15,000 to 20,000 guerillas have until next Friday to gather at 16 assembly points scattered around the country after first reporting to 24 rendezvous sites near their operational areas. All forces are allowed to keep their arms but any troops that have not reported by Jan. 4 will be regarded as illegal.

The Rhodesian Police, known as the British South African Police, will be responsible for law and order but Soames has the power to call on either of the rival armies to put down any fighting.

There will be three layers of monitoring forces in the Patriotic Front areas. At the top will be a lieutenant colonel with four officers and noncommissioned officers at each of five operational areas. They will be joined by a Patriotic Front liaison officer. The 16 assembly points will each be monitored by one officer and 16 soldiers, while an officer and nine soldiers will be responsible for each of the 24 rendezvous points.

About 550 Commonwealth troops will monitor the Rhodesian security forces, estimated to be twice as large as the Patriotic Front's forces.

The Rhodesians will be observed in 66 sites, involving four levels of command, as well as two air bases.

Later seven major border crossing points into Rhodesia from Zambia, Mozambique, Botswana and South Africa are also to be monitored.

There was little reaction in Rhodesia yesterday to the death, reportedly in an automobile accident, of Patriotic Front Military leader Josiah Tongogara. A British military spokesman said the cease-fire command was hoping Tongogara's death would not have any effect on the implementation of the truce, but he said it would take a while to see.

It was the first fatality among Front officials since the London Conference but Rhodesia on the road to a settlement. However, shots have been fired in Salisbury at relatives of guerilla coleader Robert Mugabe and at Cephas Msipa, an official in Joshua Nkomo's wing of the Patriotic Front.