More than four months of fighting in South Sudan

JUBA - Here is a timeline of more than four months of fighting in the world's newest nation, South Sudan, where the army has been fighting rebels loyal to sacked vice president Riek Machar.

The conflict, which started in the capital Juba before spreading to other key states in the country, has taken on an ethnic dimension, pitting President Salva Kiir's Dinka tribe against militia forces from Machar's Nuer people.

The fighting has so far cost thousands of lives and driven nearly one million people from their homes.

--DECEMBER 2013--

- 15: Heavy gunfire erupts overnight in Juba, where tensions have run high since Machar was fired in July. Kiir denounces a coup and says Machar is behind it. Machar denies three days later.

Fighting spreads to several states.

--JANUARY 2014--

- 9: The US, which backed South Sudan's independence in 2011, warns that its young democracy risks "shattering".

- 10: Government troops recapture the key northern city of Bentiu, capital of oil-rich Unity State, which fell into the hands of rebels on December 22.

- 15: Uganda acknowledges for the first time that its soldiers are fighting with the South Sudanese army.

- 18: Government forces recapture the key town of Bor, the capital of eastern Jonglei State, which had changed hands several times since mid-December.

- 20: The army says it has seized back full control of Malakal, the capital of the oil state of Upper Nile and the last major settlement under rebel control.

- 23: Meeting in Addis Ababa, government and rebels sign a ceasefire agreement. However, fighting continues.

--FEBRUARY--

- 18: Rebels launch a major assault on Malakal.

- 27: Human Rights Watch says war crimes have been committed by all sides.

--MARCH--

- 12: The African Union launches a probe into those responsible for atrocities since the conflict started.

--APRIL--

- 2: New peace talks, launched in February, are paused until the end of April.

- 15: Machar vows to attack the capital and target oil fields, warning the conflict will not end until Kiir is removed from power.

- 15: Rebels wrest back control of Bentiu and issue an ultimatum to oil companies to shut down production.

- 17: At least 58 civilians are killed in an attack by some 350 young armed men on a UN base in Bor sheltering thousands of displaced civilians.

- 21: The United Nations accuses Machar's gunmen of massacring "hundreds" of civilians because of their ethnicity when they captured Bentiu.