South Africa's ruling African National Congress (ANC) said on Monday it would sue opposition politician Julius Malema after he threatened to remove President Jacob Zuma's government with the "barrel of a gun".
Malema told Al Jazeera television on Sunday that the ANC used violence to suppress dissent, citing an incident last year when members of his radical Economic Freedom Fighters (EFF) party were ejected from parliament after heckling Zuma.
"We will run out of patience very soon and we will remove this government through the barrel of a gun," said Malema, Zuma's one-time protege and former ANC youth leader.
"Part of the revolutionary duty is to fight and we are not ashamed if the need arise for us to take up arms and fight," Malema said.
EFF protest marches were often met with violent resistance by security forces, he said.
The ANC said it would pursue legal action against Malema.
"These remarks are a call to violence, are inflammatory, treasonable and seditious and should be treated with extreme seriousness," the ANC said in a statement.
"The ANC calls on state authorities to urgently investigate this matter and act against such conduct."
South Africa is holding local government elections on August 3. The EFF and main opposition Democratic Alliance are expected to make inroads into majorities held by the ANC in large metropolitan areas, including the capital Pretoria.
Malema has accused the ANC of failing to redress the inequality between blacks and whites since Nelson Mandela swept to power on a wave of optimism at the end of apartheid in 1994.
The EFF was launched in 2013 and won six percent of the vote in national elections the following year. It has pledged to curb white economic power by nationalising mines and seizing land.
Its members dress in red berets and hard hats but do not carry weapons.