Lesotho's High Court will rule on whether Prime Minister Thomas Thabane can claim immunity from a charge he murdered his estranged wife prior to marrying his present spouse, a lower court has decided.

Thabane on Monday appeared in the magistrates court in the capital, Maseru, for a rescheduled hearing but he was not formally charged.

The 80-year-old had initially been scheduled to hear the charges on Friday but left for South Africa, which surrounds the mountainous kingdom, for what aides said was a medical appointment.

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The leader is suspected of involvement in the murder of his wife at the time, Lipolelo, who was shot dead in June 2017, two days before he took office for a second stint as prime minister and two months before he married his current wife, Maesaiah.

Maesaiah Thabane, 42, has also been charged with the murder and police suspect her of ordering assassins to do the job. Both deny any involvement.

Thabane's no-show for the preliminary appearance on Friday prompted police to warn they could issue an arrest warrant.

His aide initially said Thabane had gone to South Africa for "routine" health checks, but later his office said he was seeking "emergency" medical attention and would appear in court on his return.

On Saturday, the police said the authorities would wait for Thabane's return to resume his case after his lawyers said they had a sick note proving that the prime minister would be "unfit" until February 27.

Al Jazeera's Fahmida Miller, reporting from Maseru, said the trial brought up questions among the public about the division of power in the country.

"So far, the defence team of the prime minister has questioned whether a sitting prime minister can actually be charged and prosecuted," she said.

"Now the question has been taken to the High Court, which will act as a constitutional court to determine it," Miller added.

"Against the backdrop of these developments in Lesotho, there have been a lot of questions over the independence of the judiciary from the executive."

The long-serving prime minister has said he will resign at the end of July because of old age, but several members of his own All Basotho Convention (ABC) party have been pressuring him to go sooner to avert a political crisis.

Lesotho, a mountain territory of two million people, has a history of coups and political instability.

Many fear a power vacuum unless the ABC can agree on a successor, and analysts expect a general election will have to be called soon.