JUBA, South Sudan -- The United States, India and other countries continued on Thursday to evacuate their citizens from South Sudan, where a fragile ceasefire appeared to hold amid fears of a return to civil war. But some locals, even those with dual U.S. citizenship, were not allowed to leave the country.

An Associated Press reporter at the airport in the capital, Juba, saw authorities refuse about 20 dual South Sudanese-U.S. citizens from leaving the country, despite the presence of three U.S. Embassy staff.

According to one of the dual citizens, if they are allowed to leave as U.S. citizens, the authorities confiscate their South Sudanese passports.

A spokesman for the U.S. Embassy did not immediately comment. The U.S. Embassy has said it was arranging flights out of the country for Americans.

South Sudanese trying to flee the country by road have reported being turned back from the border.

A convoy of Ugandan troops that entered South Sudan on Thursday to evacuate citizens was met by an attempted ambush that left three soldiers with minor injuries, Ugandan army spokesman Paddy Ankunda tweeted.

Other countries were arranging flights for their citizens. India's external affairs minister, Sushma Swaraj, announced that two aircraft had landed in Juba for evacuations.

Other evacuees have already landed in neighbouring Kenya and Uganda and elsewhere.

Germany's foreign office said those evacuated on Wednesday included three wounded Chinese peacekeepers from the U.N. mission in South Sudan and citizens from Britain, France, Poland, Norway, Australia, Canada, Kenya and other countries.

A fourth wounded Chinese peacekeeper with leg injuries was airlifted Thursday to Uganda.

"We are all shocked by that, and we condemn strongly this attack," said the Chinese ambassador to Uganda, Zhao Yali.

About 40 other Chinese nationals were brought to Uganda on another flight Thursday.