By CELEAN JACOBSON, Associated Press Writer

JOHANNESBURG -- Frans "Ting-Ting" Masango, a former guerrilla activist once sentenced to death for treason against the apartheid government, has died, South Africa's ruling African National Congress party said Monday. He was 51.

Masango died in Pretoria on Friday after battling diabetes, the party said in a statement.

"We dip our revolutionary banner in honor of this distinguished cadre and a selfless combatant who sacrificed immensely to the democratic order we live in today," the ANC said.

Masango was part of an ANC underground military unit that operated inside South Africa in the mid-1980s and carried out attacks against the apartheid regime, including assaults on policemen and planting bombs.

He was captured in 1986 along with Jabu Masina, Neo Potsane and Joseph Makhura and faced numerous charges including murder, treason and terrorism.

The four were held in solitary confinement for many months before being brought to trial, which was held in the small town of Delmas, east of Johannesburg.

The men were dubbed the "Delmas Four" and their trial attracted international attention.

The four did not participate in their own defense as they refused to recognize the authority of the court while it upheld minority rule. They maintained they were soldiers fighting a just war and in a defiant moment wore full combat gear to their sentencing.

Masango, Masina and Potsane were sentenced to death in 1989; Makhura was sent to Robben Island, the famous prison where Nelson Mandela, the country's first black president, was held.

The four were released in 1991 after the ban on the ANC was lifted, and an account of their experiences has become an award-winning book in South Africa.

Makhura said Monday that the men had remained close and while they knew Masango was sick, they did not expect him to die so soon.

"It is very sad. We went through so much together," he told The Associated Press.

Masango was born in 1958 in Mamelodi, a township outside Pretoria. He participated in the 1976 Soweto uprising before fleeing into exile. While in Angola he received military training and was sent back to South Africa in 1985.

After the end of apartheid in 1994 he worked as a radio journalist. He was elected a member of parliament after this year's elections.

Masango is survived by his wife and three children. A funeral is expected to take place Saturday.