KwaZulu-Natal health MEC Sibongiseni Dhlomo has issued an ultimatum to striking doctors, calling on them to return to work on Friday or face the music.

"We as the department of health are designated as an essential service provider and therefore find the action of these health professionals [to be] disrupting service delivery and compromising patients' lives," Dhlomo told reporters.

Notices had been sent to all hospitals calling on striking doctors, dentists and pharmacists to resume their duties no later than 8am, he said.

Dhlomo said this week's stay-away action by doctors protesting about their salaries was "extraordinary".

His department was preparing a court interdict to force the striking health professionals to end the strike.

Health Minister Aaron Motsoaledi and the provincial cabinet were backing the court bid, said Dhlomo.

He said that he was aware that the Health Professions Council of South Africa (HPCSA) was concerned about the illegal strike and that possible charges of professional misconduct and placing the profession into disrepute could be laid.

During visits to different hospitals, the MEC found that 90 percent of doctors, dentists and some pharmacists were not at their areas of work.

He said the department had been more than reasonable in dealing with the unprotected strike.

"This situation is untenable, we cannot continue to put the lives of our people in danger and the government will act," he said.

Dhlomo said people had died due to the unavailability of doctors, although he was unable give the number of people who died as a result of the strike.

The department of health had also received information from the National Intelligence Agency that the strike was no longer about salaries.

"It is becoming clearer that this strike action is deeper than what the eye can see. Here we have people who continue striking while their leaders or unions are busy discussing the offer that has been tabled."

He said certain groups of doctors had continued to undermine the process of negotiations.

The strike over pay and working conditions started in KwaZulu-Natal four days ago and had crippled public health institutions in urban areas such as Durban and Pietermaritzburg.

Some doctors in other provinces had also stayed away from work.

While the Congress of SA Trade Unions welcomed the pay offer announced by Motsoaledi on Wednesday, the striking doctors in KwaZulu-Natal had rejected it and not returned to work.