Sporadic gunshots were heard in the area of Tonping, the U.S. Embassy said on its Twitter feed, quoting U.N. radio.

It urged its citizens to stay indoors.

Women and children carrying bags, kettles, pots and basic belongings arriving at a U.N compound to seek shelter could be seen in pictures posted on the U.N. mission in South Sudan (UNMISS) Facebook page.

"As of early Tuesday morning, an estimated 10,000 civilians have received protection in the two UNMISS compounds in Juba," UNMISS said in a prepared statement.

Toby Lanzer, a senior U.N. official in Juba, tweeted that 16,000 people had gathered at the bases as the day wound down.

A clinic at one compound had admitted 39 civilians for medical treatment, including five children, UNMISS said.

In a televised address Monday, South Sudan President Salva Kiir blamed soldiers loyal to his sacked deputy Riek Machar for starting the fighting Sunday evening.

Dressed in fatigues, he said the government was in full control of the capital and announced a nighttime curfew.

Ten people were arrested in connection with the foiled coup, according to a statement posted Tuesday on the South Sudan government website.

Tensions have been high in South Sudan since Kiir dismissed his entire Cabinet, including his deputy Machar, in July.

The move further inflamed deep-running tensions between Kiir's Dinka community and Machar's Nuer community.

South Sudan formally split from Sudan in 2011 following a referendum, after decades of conflict. Numerous armed groups remain active in the oil-rich country.

The UNMISS statement said Hilde F. Johnson, special representative of the U.N. secretary-general, called on "all parties in the current situation to refrain from any community-motivated violence."

"At a time when unity among South Sudanese is more needed than ever, I call on the leaders of this new country and all political factions and parties, as well as community leaders to refrain from any action that fuels ethnic tensions and exacerbates violence," Johnson said.

Juba's international airport remained closed. And with phone networks sketchy, embassies were turning to social media to stay in touch with their citizens.

The U.S. Embassy said it remained closed and consular services were temporarily suspended.

The British Embassy called on its citizens to stay home and avoid unnecessary movement.

In a statement, the African Union said it was "deeply concerned" about the events in South Sudan, urging the government, leadership and other stakeholders to exercise maximum restraint and avert any further escalation.