Key dates since country's 2011 independence

As it struggles to end the war and cope with famine, the world's newest nation this weekend cancelled its fifth independence celebrations.

- 2011: Independence -

On July 9, South Sudan's President Salva Kiir proclaims independence before tens of thousands of jubilant citizens and several foreign leaders.

Southern Sudan split from Sudan after six years of autonomy and decades of civil war, which lasted from the late 1950s to 1972, and then again between 1983 and 2005, leaving millions dead.

A peace accord signed in 2005 by north and south opens the way to a referendum on independence, in which nearly 99 percent of southerners vote for secession.

However numerous disputes remain between the two countries, notably on how to share oil revenues, the tracing of their common border and the status of disputed regions like Abyei.

- 2012: Oil -

AFP/File / Tony Karumba

Spent munitions lie on the ground at an abandoned oil treatment facility at Thar Jath in Unity State, South Sudan in February 2015

From March to May deadly clashes pit the armies of Juba and Khartoum against each other in the oil fields of Heglig, an area to which both countries lay claim.

South Sudanese troops briefly occupy the area, which accounts for half of Sudan's crude oil production.

Upon independence, South Sudan inherited three quarters of Sudan's oil reserves, but, being landlocked, depends on the north's infrastructure to export crude.

With bitter arguments over pipeline transit costs, the north confiscates part of the oil and Juba in response halts its production in January. More than a year later, in April 2013, oil from the south starts flowing again through Sudan.

- 2013: Civil war -

On December 15, heavy gunfire erupts in Juba. Tensions had spiked after Riek Machar, from the country's second-largest ethnic group, the Nuer, was fired as vice-president in July.

Kiir, from the majority Dinka people, accuses Machar of a failed coup.

AFP/File / Albert Gonzalez Farran

UN experts say Riek Machar (left) and Salva Kiir are both responsible for most of the violence committed during the civil war

Machar denies this and accuses Kiir of starting the war by launching a purge. The fighting is marked by ethnic massacres in Juba, spreading to several states.

The northern city of Bentiu, capital of oil-rich Unity State, Malakal in Upper Nile, and Bor in Jonglei are among the main centres of the fighting. All three are razed by fighting.

- 2015: Peace accord -

On August 17, Machar signs a peace accord in Addis Ababa providing for a ceasefire and a power-sharing mechanism.

On August 26, Kiir signs the accord, while expressing "serious reservations" on several of its provisions.

- 2016: Unity government -

On April 26, Machar finally returns with members of his security forces to Juba, where he is sworn in as vice-president of a unity government. Three days later, Kiir forms his transitional government. Fighting continues.

On July 8, as many as 150 fighters are killed in a shootout between soldiers and former rebels in Juba that begins near the presidential palace as Kiir and Machar were due to address the press with a joint message of peace ahead of independence day.

AFP/File / Albert Gonzalez Farran

A UN peacekeeper from Rwanda walks through the remnants of a looted and burnt clinic in the UN Protection of Civilians site in Malakal, on February 26, 2016

On July 10, fighting erupts again in South Sudan's capital with former rebels and government soldiers exchanging heavy fire.

In New York, the UN Security Council urges the two rivals to call a ceasefire, redeploy their forces outside the capital and implement the peace agreement.

But intense battles resume July 11 involving tanks, helicopter gunships and artillery and mortar fire, sending thousands of people fleeing to safety.

There were no immediate details of casualties.