Lesotho's Prime Minister Thomas Thabane, who was to be charged with the murder of his estranged wife, has failed to appear in court.

Thabane, 80, who left the mountainous kingdom of Lesotho on Thursday, had a pre-arranged doctor's appointment in South Africa's capital, Pretoria, his private secretary said on Friday.

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"He is not attending court, he has gone for a medical check-up in South Africa," Thabo Thakalekoala told AFP news agency, adding it is a "routine" medical check.

Thabane was scheduled on Friday to face a murder charge in connection with the killing of Lipolelo Thabane, who was shot dead in June 2017. His court appearance will now be rescheduled.

"We shall wait until he becomes available and we shall arrange that he comes here and appears before the court of law and be formally charged," Deputy Commissioner of Police Paseka Mokete told Al Jazeera.

The long-serving prime minister announced on Thursday he would quit office by the end of July because of old age.

Thabane is accused of having acted "in common purpose" in the June 2017 killing by unknown assailants of Lilopelo, 58, then his wife.

His current wife, Maesaiah Thabane, 42, who he married two months after Lipolelo's death, has already been charged with ordering Lipolelo's murder but is currently out on bail.

'Complex case'

Al Jazeera's Fahmida Miller, reporting from outside the court in the capital, Maseru, said the complex case has become more complicated now that the prime minister is in South Africa.

"There were rumours circulating earlier that he had fled the country, but his private secretary says this is not the case, that the prime minister is willing and ready to be in court, just not today," she said.

His son also dismissed the rumours.

"He has not fled the country, he has gone to South Africa to see a doctor," Potlako Thabane told Reuters News Agency.

In 2017, Lipolelo and Thomas were going through an acrimonious divorce. An unknown assailant shot her dead in her car.

Her friend, Thato Sibolla, who was travelling with her in the vehicle, escaped with gunshot wounds and has since fled to neighbouring South Africa fearing for her life.

The death shook the landlocked kingdom of Lesotho, which is entirely surrounded by South Africa.

"We have a very strong case against the prime minister ... which we are going to present before the court of law which actually implicates the prime minister to the crime," Mokete said.