The attack, in which Patrick Bergin, 33, from Helston, Cornwall, died, comes two weeks after 23 people died in the crashes of two United Nations planes.
Wednesday's attack, blamed on Unita rebels, also claimed the lives of a Brazilian civil engineer, Mario Trepechio, and two Angolan guards.
The men, who were employed in Cuango, a mine some500km east of the capital, Luanda, were employed by Ashton Mining, an Australian company. At the time of the ambush, the men were travelling from the Tzua mining area to the project's operational headquarters at Luzamba in Lunda Norte province.
Ashton's chief operating officer, Douglas Bailey, said: "We are all deeply saddened by the loss of life on the project."
Ashton has instructed its London-based international security adviser, Control Risks Group Limited, to speed up a planned review of security arrangements in Angola.
The attack is the latest in a series to be blamed on Unita, the rebel movement fighting the Angolan government for control of the vast southern African country's diamond mines. Unita (the National Union for the Total Independence of Angola) currently has the upper hand in a renewed struggle that has destroyed a UN peace plan to end a 30-year civil war.
In a rare gesture to the UN, Unita yesterday said it would co-operate with the search for the wreckage of the UN planes, which went down on 26 December and on Saturday.
Last November, Unita forces attacked the Yetwene mine partly owned by the Canadian company DiamondWorks.
A number of people were killed, including two Britons. Four people were captured, including a 26-year-old English geologist, Jason Pope.
Unita has, until now, maintained - despite UN protests to the contrary - that it has yet to receive a formal request for assistance from the world body in finding the two planes.
The rebel movement and the Angolan government, which on Wednesday pledged its full support in a rescue mission, have accused each other of shooting down the two C-130 transport aircraft.
UN officials said the first UN-leased Hercules to crash had 14 passengers and crew on board. The second plane was carrying nine passengers and four crew.