(CNN) -- U.S. Secretary of State John Kerry is sending a special envoy to South Sudan following an escalation of violence in the world's newest nation.
Ambassador Donald Booth, the special envoy to Sudan and South Sudan, headed to the area Friday.
"Now is the time for South Sudan's leaders to rein in armed groups under their control, immediately cease attacks on civilians, and end the chain of retributive violence between different ethnic and political groups," Kerry said in a statement. "The violence must stop, the dialogue must intensify."
Also on Friday, National Security Adviser Susan Rice recorded an audio message to the people to South Sudan.
"I ask each of you to make the choice for peace -- make the choice for a unified and cohesive South Sudan," she said. "Make this choice for yourselves and your children."
Attackers killed two Indian army peacekeepers in South Sudan and wounded a third one in the chest, the United Nations said Friday.
At least two of the 30 civilians who took refuge at the United Nations' Akobo base were killed in the attack Thursday, said Joseph Contreras, the U.N. spokesman for South Sudan. It could have been as many as 20 who died in that attack U.N. officials estimated.
Their remains will be taken to the capital of Juba.
Deadly clashes have raged South Sudan for days after a reported coup attempt in the capital over the weekend
President Salva Kiir blamed soldiers loyal to his former vice president, Riek Machar, for starting the violence.
Casualties are in the hundreds, including soldiers, the government said.
The government of neighboring Kenya will send troops into South Sudan to help evacuate 1,600 Kenyan citizens, presidential spokesman Manoah Esipisu said.
An official from South Sudan's ruling party, who has just left the country, said the U.S. is not doing enough.
"There was a lot of presence of troops in the city. There was a lot of injured, displaced people. Gunshots heard every two minutes, a lot is at stake, a lot needs to be done," said Choul Laam, chief of staff for the secretary general of the ruling SPLM Party.
"President Barack Obama made a statement and is dispatching a special envoy to the area. I believe that's not enough. A lot of dialogue needs to be taking place. A lot of convincing needs to be taking place."
Obama sent 45 service members to South Sudan to support U.S. personnel and the American Embassy.
"In 2011, millions of South Sudanese voted to forge a new nation, founded on the promise of a more peaceful and prosperous future for all of South Sudan's people," Obama said in a prepared statement. "In recent years, against great odds, South Sudan has made great progress toward breaking the cycle of violence that characterized much of its history.
"Today, that future is at risk. South Sudan stands at the precipice. Recent fighting threatens to plunge South Sudan back into the dark days of its past," the President said.
Tensions have been high in South Sudan since Kiir dismissed his entire Cabinet, including Machar, in July. The move inflamed deep tensions between Kiir's Dinka community and Machar's Nuer community.
U.N. officials have said they are worried the recent fighting is based on ethnic divisions, but the government has disputed that assertion.
Eleven people have been arrested in connection with the foiled coup
CNN's Zain Verjee and Clare Hayes contributed to this report.