South African police on Wednesday hailed hefty sentences imposed on 22 illegal miners, calling the move "a landmark moment" in the fight against illegal mining in the country.

This came after the Virginia High Court in Free State Province sentenced 22 convicted illegal miners to lengthy prison terms ranging from 20 to 22 years.

This is the first time in South Africa that illegal miners get lengthy prison terms.

"We hope that this precedent set by our courts will not only serve as a deterrent, but will also help us in our efforts to combat illegal mining even in other upcoming cases," Police Lieutenant General Mthandazo Ntlemeza said in a statement.

The 22 miners were arrested in April 2014 for illegal mining operation that started in August 2012 at Masimong Mine in Welkom, Free State Province.

They were arrested during an operation conducted by a security company and the Hawks, a special anti-crime unit while the criminals illegally occupied a closed mine. Initially, all convicts were facing 843 charges. However, they were cleared on 266 charges and were found guilty on 577 charges on February 20, 2017.

South Africa's disused shafts are a draw card for gold diggers from neighboring Mozambique, Lesotho and Zimbabwe.

According to the South African Chamber of Mines, over six billion rand (about 460 million U.S. dollars) is lost through illegal mining annually in the country.

About 70 percent of illegal miners are illegal immigrants, and about 14,000 people are involved in illegal mining in South Africa, the chamber says.

Illegal mining is also blamed for human tragedies. In the most infamous case to date, 91 illegal miners perished after a fire broke out underground in a disused section of Harmony Gold Mining's Eland shaft in South Africa's Free State goldfields in June 2009.

The case attracted international attention and led to crackdown attempts by the South African government.