(Reuters) - A conflict raging in Sudan is rattling neighbouring countries and worrying the United States and others for reasons ranging from concern about shared Nile waters and oil pipelines to the shape of a new government and a new humanitarian crisis in the making.
Sudan, which relies heavily on foreign aid, is no stranger to conflict. But this time fighting is tearing apart the capital instead of a remote corner of a nation, which lies in an unstable region bordering the Red Sea, Sahel and Horn of Africa.
Five of Sudan's seven neighbours - Ethiopia, Chad, Central African Republic, Libya and South Sudan - have faced political upheaval or conflict themselves in recent years.
The fighting that erupted between the army and paramilitary Rapid Support Forces (RSF) on April 15 in Khartoum has derailed an internationally backed plan for a transition to civilian rule after the ousting in 2019 of Omar al Bashir, the Islamist president who had himself seized power in a 1989 coup.
The conflicts pits General Abdel Fattah al-Burhan, the head of Sudan's ruling council who commands the army, against the irregular RSF forces led by the wealthy, one-time militia leader General Mohamed Hamdan Dagalo, better known as Hemedti, who is Burhan's deputy in the council.
WHAT'S AT STAKE FOR REGIONAL STATES?
EGYPT - The histories of Egypt, the most populous Arab state with a powerful army, and Sudan are intertwined by politics, trade, culture and shared Nile waters. Cairo has worried about political upheaval to its south since the 2019 uprising that toppled Bashir. Egyptian President Abdel Fattah al-Sisi, who also took office in a military power grab, is close to Burhan.
Sudanese are by far the largest foreign community in Egypt, numbering an estimated 4 million people, including about 60,000 refugees and asylum seekers.
Egypt and Sudan, which both rely on the Nile for fresh water, are concerned about threats to their supplies from the Grand Ethiopian Renaissance Dam (GERD) project upstream on the Blue Nile. The two nations have pushed to regulate the Ethiopian dam's operation. Any tension in ties between Khartoum and Cairo could disrupt their efforts to secure a deal.
LIBYA - Sudanese mercenaries and militia fighters have been active on both sides of the civil conflict that split Libya after 2011. In recent years, many Sudanese fighters have returned to Sudan, contributing to tensions in Sudan's western Darfur region, where another conflict raged for years and fighting continued after a deal with some rebel groups in 2020.
Sudan has also been a departure point and a transit route for migrants seeking to head to Europe via Libya, where people traffickers have taken advantage of the conflict and political turmoil.
CHAD - Sudan's western neighbour Chad, a poor nation which hosts about 400,000 displaced Sudanese from previous conflicts, has seen about 20,000 more refugees arrive from Sudan since the latest fighting began, according to the United Nations.
Chad worries about the crisis spilling across the border to areas where it hosts the refugees, most of whom are from Darfur. During the Darfur conflict, Chad faced cross-border raids from Sudan's Arab militias, known as the Janjaweed, which morphed into the RSF. The raiders attacked Darfur refugees and Chadian villagers, seizing livestock and killing those who resisted.
Chad's government said it disarmed a contingent of 320 paramilitary forces that entered its territory on Monday.
Chad also worries that Russia's Wagner Group private military contractors in neighbouring Central African Republic, who are reported to have close ties with RSF, could back Chadian rebels threatening N’djamena's government.
Wagner denies having any activities in Sudan.
GULF ARAB STATES - Wealthy oil producers Saudi Arabia and the United Arab Emirates have long sought to shape events in Sudan, seeing the transition from Bashir's rule as a way to roll back Islamist influence and stabilise the region.
Investors from both countries have deals to invest in a range of projects from agricultural projects, where Sudan holds vast potential based on large irrigated areas, to an airline and strategic ports on its Red Sea coast.
SOUTH SUDAN - South Sudan, which seceded from Sudan in 2011 after a civil war lasting decades, exports its oil output of 170,000 barrels per day via a pipeline through its northern neighbour.
Analysts say neither side in Sudan's conflict has an interest in disrupting those flows but South Sudan's government said this week fighting had already hampered logistics and transport links between the oilfields and Port Sudan.
Sudan also hosts 800,000 South Sudanese refugees. Any mass return could put further strains on efforts to supply vital aid to more than 2 million displaced people in South Sudan who have fled their homes inside the country because of civil strife.
ETHIOPIA - Skirmishes periodically flare along disputed parts of Sudan's border with Ethiopia. Analysts say either side could take advantage of Sudan's unrest to press their objectives.
When war erupted in Ethiopia's northern Tigray region in 2020, tensions surfaced over the fertile but contested Al-Fashqa border and drove more than 50,000 Ethiopian refugees into already impoverished parts of eastern Sudan.
Ethiopia will also be watching developments given tensions over the $4 billion GERD dam, which Sudan says could present a threat to its own Nile dams and its citizens.
ERITREA - Sudan hosts more than 134,000 refugees and asylum seekers from Eritrea and is the main route for Eritreans fleeing forced conscription by Asmara government's repressive rule.
Many Eritrean refugees in northern Ethiopia fled from their camps during the Tigray war between 2020 and 2022. Eritrean refugees in Sudan could face a similar plight if any conflict beyond Khartoum escalates.
WHAT ARE THE CONCERNS OF WORLD POWERS?
RUSSIA - Moscow, which has long sought warm water ports for its navy, secured a deal with Bashir for Sudan to host a naval base and Sudan's military leaders have said this remains under review. In 2020, Russian President Vladimir Putin approved the creation of a Russian naval facility in Sudan capable of mooring nuclear-powered surface vessels.
Western diplomats in Khartoum said in 2022 that Russia's Wagner Group was involved in illicit gold mining in Sudan and was spreading disinformation. Two years earlier, the United States imposed sanctions on two companies operating in Sudan that it linked to Wagner boss Yevgeny Prigozhin.
In a statement on April 19, Wagner denied it was operating in Sudan, said its staff had not been there for more than two years and said it had no role in the latest fighting. It said it was responding foreign media inquiries "most of which are provocative".
In February 2023, Russian Foreign Minister Sergei Lavrov met officials in Sudan during an African tour seeking to expand Moscow's influence at a time when Western nations have sought to isolate Moscow with sanctions over its invasion of Ukraine.
THE UNITED STATES AND THE WEST - The United States, like other Western powers, was happy to be rid of Bashir, who was charged with genocide and war crimes by the International Criminal Court over the Darfur conflict.
But critics say Washington was slow to swing behind a transition towards elections. Sudanese hopes for democracy were shattered when Burhan and Hemedti staged a coup in 2021.
The latest fighting is expected to derail any swift return to civilian rule with neither of the two opponents in Khartoum showing any readiness for compromise.