Presidential Guard troops stormed the compound of former Vice President Riek Machar Tuesday after President Salva Kiir Mayardit accused him of masterminding an attempted coup in the fledgling state's capital, Juba, a clash that could affect the country's oil industry, its economic lifeline.

The oil fields are some distance to the north of the ramshackle capital of a country that became independent from Sudan July 9, 2011, under a 2005 peace agreement that ended decades of civil war between the Muslim north and the largely Christian south.

But there are fears the fighting around Juba could spread to the oil fields that produce about 200,000 barrels per day as the global energy market grapples with major production losses in anarchy ridden Libya.

Fighting broke out in Juba late Sunday between rival army factions following months of a power struggle between Kiir and Machar, who come from rival ethnic groups.

Details of the clashes remain sketchy, and there's no clear account of casualties from clashes in which mortars and heavy machine guns were used.

But Kiir, dressed in general's uniform instead of his usual business suit and trademark black Stetson, addressed the nation on television Monday and claimed military units allied with Machar attempted to seize power and had been crushed.

But there was widespread speculation that Kiir may have moved first, pre-empting Machar's alleged plot before it could be mounted.

The main clashes were in two military bases, the Bilpam barracks near the Juba airport and the Jebel barracks south of the city where the Presidential Guard is based.

Troops loyal to Kiir, led by the elite Presidential Guard, prevailed. But sporadic gunfire could still be heard throughout the city Monday and Tuesday.

Machar was in hiding as Kiir launched a nationwide hunt for his former deputy. Several politicians allied with Machar were reportedly arrested, but he remained at large.

The raid on his Juba compound, defended by Machar's bodyguards, apparently failed to turn up any evidence of his whereabouts.

Kiir, leader of the Sudan People's Liberation Movement and a guerrilla leader during the civil war, belongs to the Dinka, the dominant tribe in the south.

Machar, an influential politician who was also one of the southern heroes of a conflict that was Africa's longest war, is from the Nuer tribe, which has often fought the Dinka in the past -- even during the civil war when both were battling the north under its military dictator.

Kiir sacked Machar as deputy president, along with the rest of his cabinet, in July, after Machar became increasingly critical of Kiir's rule, claiming he was becoming a dictator, amid rumblings within the ruling party that observers feared signaled tribal conflict.

Machar also let it be known he planned to run for president in elections scheduled for 2015.

The current violence underlined tribal rivalries that have long plagued the region, indeed most of the continent. Throughout the 1990s, the rebel SPLM was fractured by factionalism, with Machar heading a splinter group that often fought pitched battles with the Dinka.

The upheaval erupted several weeks ago after South Sudan resumed pumping oil following a 15-month shutdown triggered by demands by the Sudanese government in Khartoum for hefty fees for transporting crude from the landlocked south to the export terminal at Port Sudan on the Red Sea.

Oil is at the center of the current dispute between north and south, just as it was a key factor in the civil war.

Most of the oilfields are in South Sudan. But the pipeline to the Red Sea terminal runs through territory controlled by Khartoum.

Both countries suffered major economic crises during the shutdown. South Sudan is seeking to secure outside investment to build a new pipeline from its oilfields through neighboring Kenya to the Indian Ocean.

But that remains a distant prospect at this time and the two Sudans will either have to find a modus Vivendi, or suffer further economic problems.

Gen. Omar al-Bashir, Sudan's president who seized power in a bloodless military coup in 1989, also faces opposition within his regime following the 2011 separation and claimed to have crushed a coup plot in 2012 amid a power struggle.

He threw several senior figures into prison, including his powerful former intelligence chief, Salah Gosh, but pardoned them in July.