The continued gunfire, including the sporadic firing of heavy weapons, resumed in the early hours of Tuesday and went into the morning as terrified residents barricaded themselves in theirs homes or were attempting to flee the city.
South Sudan's Under-Secretary for Health Makur Korion said on local radio that at least 26 people had so far been killed in the violence. At least 130 more are reported to have been wounded.
"We can still hear sporadic shooting from various locations. The situation is very tense," Emma Jane Drew of the British aid agency Oxfam told AFP by telephone from Juba.
The fighting began late on Sunday, and South Sudan's President Salva Kiir has accused troops loyal to his arch-rival, former vice president Riek Machar who was sacked from the government in July, for attempting a coup.
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President Kiir had also said Monday that his troops were "in full control of the security situation in Juba" and imposed an overnight curfew on the city.
Thousands of civilians have reportedly taken refuge at UN offices, and an AFP reporter said many residents living in areas close to military bases were using any lull in the fighting to flee for safer areas, although many said they were too afraid to move.
"We had wanted to go out and buy food from the market, but how can you go with the shooting? I am staying at home with my children."
There were unconfirmed reports of troops conducting violent house-to-house searches.
"We have heard unconfirmed reports of house to house military checks of civilians including the use of brutality and violence, though this is unconfirmed," Oxfam's Drew said, raising concerns of an ethnic dimension to the fighting.
"It is a very strong possibility. We have certainly received reports of that, but we're locked in the compound, relying on word of mouth," she said.