Former guerrillas of the army once led by current Prime Minister Robert Mugabe went on what police describe as a "drunken" rampage yesterday in a sparsely settled area, killing a white government employe and opening fire on five other whites, including three British military advisers.

At the same time, in the troubled Chitungwiza township near the capital, a black died after confused shooting involving former guerrillas of Mugabe's force and that of Home Affairs Minister Joshua Nkomo. About 4,000 men from each of the rival armies are quartered in fenced-off compounds in the sprawling settlement 12 miles south of Salisbury, awaiting integration into the Zimbabwean Army or resettlement.

The incidents 90 miles east of Salisbury, in the Mtoko area, were the most violent since July when two policemen were killed there. Police said in five ambushes yesterday, one other white was injured, a black police constable was assaulted and a black detective had his car stolen.

The fighting in Chitungwiza seemed to be the closest the rival guerrilla groups have come to a direct clash since independence from Britain April 18. All transport to the satellite township was halted last night as firing continued.

Mugabe was known to be deeply concerned about the situation in Chitungwiza. The incidents coincided with a visit by a British business delegation, whose members happened to be advised by British diplomats today not to believe everything they read in the British press about unrest in Zimbabwe.

Since independence, Zimbabwe has been sustained, if low-key political and guerrilla violence, much of it involving the 35,000 bush fighters who reported to isolated and inhospitable assembly camps after a cease-fire last December. Eight whites and 14 blacks have been killed and hundreds more injured in grenade attacks and shooting incidents.

The latest violence, however, has more serious overtones. In Mtoko, yesterday's shooting demonstrates the inability so far of the central authorities to prevent ill-disciplined guerrillas from virtual rebellion against government control.

Disillusioned with their meager fruits of independence, the guerrillas virtually run their own fiefdoms, beyond the control of the new national Army and the police. Yet Mugabe's ability to attract foreign aid and investment may depend on his handling of the former guerrillas. f

The Chitungwiza incident could have equally profound ramifications. Mugabe moved the guerrillas into the huge township as part of a plan to ease their discontent and give them some taste of city life before they are inducted into the national Army, whose British-assisted formation is going slowly. Many residents expressed fears that the move would lead to further violence, since the tribally and ideologically divided contingents are encamped only about three miles apart, within mortar range.

These fears now seem to have been confirmed and Mugabe was known to be working through his senior aides to head off a real confrontation.

The British military team here has clearly been angered by the incidents, although senior officers acknowledged that the ambushes were not directed specifically at the British presence and had been caused by end-of-the-month drinking sprees. The former guerrillas are paid about $160 a month and have little to spend it on except drink. In many cases they have refused to earn their pay on government agricultural schemes.