Pretoria - President Kgalema Motlanthe has joined the international community in expressing outrage and condemnation at the assassination of Guinea Bissau President Joab Vieira.
"South Africa and indeed the entire Southern African Development Community (SADC) region were indeed shocked to learn of the callous murder of the democratically elected President of Guinea Bissau," President Motlanthe, who is also the current SADC Chairperson, said in a statement on Tuesday.
The United Nations, the African Union and the Economic Community of West African States (Ecowas) have also condemned the killing.
President Vieira was apparently gunned down by soldiers while trying to flee his house on Monday after the military had blamed him for the death of Army Chief-Of-Staff Tagme na Waie in a bomb blast on Sunday.
The incident came only hours after General Batista Tagme Na Wai, the country's Army Chief was killed in a bomb attack.
According to Guinean officials, Mr Vieira was killed when he refused to accompany Angolan diplomats who had earlier taken his wife somewhere for her safety.
President Motlanthe said no amount of words could fully express the international community's condemnation of such "heinous acts."
He said the SADC welcomed the assurance from the Guinea Bissau authorities that despite these developments, the democratically-elected government remained in place.
"Accordingly, we welcome the commitment of the Guinea Bissau armed forces to abide by and respect the rule of law and the Constitution of Guinea Bissau," he said.
UN Secretary General Ban Ki-moon also voiced his concern at the threat to stability in the West African country following the attack.
He called for urgent calm and restraint and for the national authorities of Guinea-Bissau to fully investigate these assassinations and bring them to justice.
Mr Ban further said he was deeply saddened and dismayed by the assassinations.
"The secretary general strongly condemns these violent acts, which have occurred soon after successful legislative elections which paved the way for enhanced UN support to the country's peace-building efforts," said a UN statement.
The AU on Monday described the killings as "cowardly and heinous attacks in a country brutalised by corruption linked to cocaine smugglers".
AU Commission Chairman Jean Ping Mr Ping said the deaths "come at a time of renewed efforts by the international community to support peace-building efforts in Guinea-Bissau.
AU's Peace and Security Council are on Tuesday holding an emergency meeting to review the situation in the country.
Media reports indicate that the ambassadors went into closed-door talks at the 53-nation body's headquarters in Addis Ababa, Ethiopia.
According to the AU's statutes, member states should be suspended in the event of an unconstitutional power change, as were Mauritania and Guinea Conakry following coups last year.
Ecowas is to send a delegation of foreign ministers to Bissau on Wednesday, according to its Chairperson Nigerian President Umaru Yar'Adua.
President Vieira seized power in 1980, before being elected President in the country's first democratic elections in 1994.
Ousted in a coup in 1999, he was re-elected in 2005, after pledging to develop the economy.
Mr Na Wai served in a junta which ousted Mr Vieira in 1999.
Rivalry between the two, which went back to a 1980s army uprising against Mr Vieira's rule, has ever since dominated politics for years.
Mr Vieira's and Mr Na Wai's deaths leave space for other political leaders to emerge, but also raise the prospect of intensified infighting between potential successors.
Their deaths may also open the way for a return by political and military figures sidelined in the power struggles of recent years.
For now, according to their constitution, the speaker of the National Assembly would succeed Mr Vieira for a limited period pending presidential elections.