South African drugs company Aspen has avoided an EU anti-trust fine after it agreed to slash prices on six cancer drugs.

The firm agreed to cut by as much as 75% the cost for medicines used for the treatment of some forms of blood cancer including leukaemia.

An investigation launched in 2017 by the European Commission found the company had abused its dominance and was at some point threatening to hike prices and even threatened to withdraw drugs if it didn't get its way.

"Today's decision gives a strong signal to other dominant pharmaceutical companies not to engage in abusive pricing practices to exploit our health systems," said Margrethe Vestager, European Commission competition chief.

The prices will return to the levels they were in 2012 and remain in force for 10 years and the company has committed to maintain the supply of drugs, the commission said.