- Army HQ and airport are major focus of fighting
- At least 270 people killed, 2,600 injured - ministry
- US-brokered ceasefire fails, RSF says to try again
- Power struggle has dashed transition to democracy
- Power cuts, water and food shortages hit residents
Sudanese troops battled waves of attacks on Wednesday by a paramilitary force trying to seize the army's headquarters, while the failure of a US-brokered ceasefire hampered efforts to evacuate foreigners and residents trapped in the capital.Continuous bombardments and loud blasts could be heard in central Khartoum around the compound housing the army HQ and also at the main airport, which has been fiercely contested and put out of action since fighting erupted at the weekend.Thick smoke billowed into the sky and the streets were largely empty in Khartoum. Gunfire rattled in the south of the city, a Reuters witness said, while the army appeared to retake a key military airport in the country's north, images on TV network al Arabiya showed.Earlier in the week, Sudan's military ruler General Abdel Fattah al-Burhan said he was operating from a presidential guesthouse within the Khartoum army HQ. Reuters could not establish whether he remained there on Wednesday."The armed forces are responding to a new attack in the vicinity of the General Command," the army said in a statement.Huddled in their homes, residents of the capital, one of Africa's largest cities, struggled with power cuts and worried how long food supplies would last."Today we were starting to run out of some essentials," said architect Hadeel Mohamed, concerned for the safety of her brother who had gone to look for food.With no signs of peace in the city before the Eid festival that marks the end of Ramadan this week, some Khartoum residents braved the bombardments to leave for the nearby state of Al Gezira, to the south, where fighting has not been reported.Violence erupted at the weekend in a power struggle between the army and the paramilitary troops known as the Rapid Support Forces (RSF). At least 270 people have died and 2,600 have been injured, Sudan's health ministry said, cited by the World Health Organization.The fighting pits military leader Burhan against RSF chief General Mohamed Hamdan Dagalo, widely know as Hemedti, following tension over a plan to integrate the RSF into the regular military.Burhan heads a ruling council installed after the 2021 military coup and the 2019 ouster of veteran autocrat Omar al-Bashir, while Hemedti was his deputy on the ruling council.The conflict risks drawing in actors from Sudan's neighbours and could play into competition between Russia and the United States for regional influence. Sudan sits strategically between Egypt, Saudi Arabia, Ethiopia and Africa's volatile Sahel region.A Reuters reporter said there was a heavy exchange of gunfire in the Jabra neighbourhood of west Khartoum, where homes belonging to Hemedti and his family are located. Hemedti's location has not been revealed since fighting began on Saturday.The RSF said in a statement on Wednesday that the army breached international law and used heavy artillery against the homes of families and citizens in Jabra.The army controls access to Khartoum, a metropolis of around 5.5 million people, and appeared to be trying to cut off supply routes to RSF fighters within the capital.Army reinforcements were brought to the city from eastern areas near the border with Ethiopia, witnesses and residents said.Foreign powers including the United States and Egypt have pushed for a ceasefire to allow residents to obtain relief and supplies, along with evacuations of foreign citizens.Both sides had agreed to a 24-hour truce from Tuesday, but there was no pause in hostilities. The army and the RSF issued statements accusing each other of breaking the truce.The RSF on Wednesday said it was again ready to observe a ceasefire from 6pm (1600 GMT). The army did not announce its own commitment.With planes smouldering on the runway of Khartoum's international airport, evacuations looked difficult for now.The US State Department said the "uncertain security situation" and the closure of the airport meant there were no plans for a US government-coordinated evacuation. Turkey has also said it could not currently evacuate.Germany halted a mission on Wednesday to fly out about 150 citizens on three Luftwaffe A400M transport planes, the Spiegel magazine reported, citing unnamed sources.Asked about the report, the German foreign ministry said all options were being assessed.Japan's Chief Cabinet Secretary said authorities were planning to use a plane from its military Self-Defense Forces to evacuate around 60 Japanese citizens.Gunmen have targeted hospitals and humanitarian workers, with reports of sexual violence against aid workers, the United Nations said. Most hospitals are out of service and health charity Medecins Sans Frontieres (MSF) said armed men raided a warehouse of supplies it operates in the west of the country.Even before the conflict, around a quarter of Sudan's population was facing acute hunger. The World Food Programme halted one of its largest global aid operations in the country on Saturday after three of its workers were killed.