* Explosions heard Monday after overnight fighting
* U.N. envoy appeals for calm
By Carl Odera
JUBA, Dec 16 (Reuters) - Fighting erupted between South Sudanese soldiers overnight around the capital and gunfire and explosions could still be heard on Monday morning, witnesses in Juba said, following months of tension after the president sacked his deputy.
Jok Madut Jok, Chairman of ...