LONDON (AP) _ Cuba is using a lethal mixture of Soviet-supplied mustard gas and nerve gases to flush out South African-backed Angolan rebels from their strongholds in remote areas, Jane's Defense weekly reported Thursday.

Prof. Aubin Heyndrickx, head of toxicology at the University of Ghent in Belgium and a United Nations expert on biological and chemical warfare, was quoted as saying his evidence that Cuba is using the gasses is based on environmental samples taken from the Angolan battle zone in April.

Jane's Defense weekly is an authoritative publication dealing with military matters worldwide.

Soil, leaf and water samples showed clear traces of mustard gas and nerve gases, Heyndrickx was quoted as saying.

The attack must have taken place in March or April, Heyndrickx was quoted as saying, because the nerve gases are extremely volatile and would not remain in the environment for longer than a few weeks.

The professor was quoted as saying he couldn't tell exactly which nerve gas was used, although he knows it is one of the three neurotoxins, Soman, Tabun or Sarin.

The report came as U.S. mediators were working on a compromise timetable for a withdrawal of 50,000 Cuban troops from Angola at talks in the Congo. South Africa has promised to pull out its troops from Angola by Sept. 1 and grant independence to South-West Africa, also known as Namibia, on condition the Cubans leave.

Heyndrickx was quoted as saying he is convinced the Cubans are continuing to uses gases in Angola to help win the war against rebels of the National Union for the Total Independence of Angola (UNITA).

''I'm sure the Cubans will go ahead with this. This is the new military tactic,'' Jane's quoted him as saying.

The UNITA rebels, backed by South Africa and the United States, have been fighting since 1975 to force the Cuban- and Soviet-backed Angolan government to share power. The rebel group controls large portions of southern Angola.

The professor was quoted as saying he has gas detection kits captured from Cuban soldiers which are designed to measure whether levels of poison in the atmosphere are toxic for man.

A University of Ghent team examined patients in UNITA field hospitals and found evidence of nerve gas attacks in 1986 and 1984, but none of those victims showed any trace of mustard gas, he was quoted as saying.