Residents of Sudan's besieged city of al-Fashir have been taking refuge in underground bunkers to try to protect themselves from drones and shells after intensifying attacks on displacement shelters, clinics and mosques.

Famine-stricken al-Fashir is the Sudanese army's last holdout in the vast, western region of Darfur as it battles the paramilitary Rapid Support Forces (RSF) in a civil war that has raged for two-and-a-half years.

The conflict, which erupted from an internal power struggle, has triggered ethnic killings, drawn in foreign powers and created a massive humanitarian crisis.

The army has been gaining ground elsewhere in Sudan, but Darfur is the RSF's stronghold where it aims to base a parallel government, potentially cementing a geographical splintering of the country.

More than one million have fled al-Fashir during an 18-month siege by the RSF, according to the UN, but it has become dangerous and expensive to leave. An estimated quarter of a million civilians remain, and there are fears of mass reprisals if the city falls.

STRUGGLE TO AVOID DRONE STRIKES

Many of those still in the city have dug bunkers for protection after repeated strikes on civilians, according to more than a dozen residents reached by phone as well as footage obtained and verified by Reuters.

The residents described avoiding drones by limiting movements and large gatherings during daytime, and not using lights after dark.

"We can only bury people at night, or very early in the morning," said Mohyaldeen Abdallah, a local journalist. "It's become normal for us."

Five residents said drones have followed civilians into areas where they gather, such as clinics. "When you're walking around you stick to the wall like a gecko so the drone won't see you go inside," said Dr. Ezzeldin Asow, head of al-Fashir's now-abandoned Southern Hospital.

At one shelter in al-Fashir's Abu Taleb school at least 18 people were killed in the week from September 30 by bombardment, a drone attack and an RSF raid, said Abdallah, who visited the site before and after the attacks.

Footage verified by Reuters showed the school's shattered ceilings and scarred walls. On the school grounds, it showed a dead body lying outside a shipping container buried in the ground to create a shelter, with sandbags around the entrance.

Neither the army nor the RSF responded to written requests or calls seeking comment on the incidents at Abu Taleb school and elsewhere in al-Fashir.

Residents captured in the footage blamed the RSF for attacks. Reuters could not independently verify who was responsible.

"They don't distinguish between civilians and soldiers, if you're human they fire at you," Khadiga Musa, head of the North Darfur health ministry, told Reuters by phone from al-Fashir.

The RSF and its allies have been blamed for waves of ethnically driven violence in Darfur during the war, with the US determining last year that they had committed genocide. Its leadership denies ordering such attacks and says rogue soldiers will face justice.

In a statement on October 12, the RSF said al-Fashir was "devoid of civilians". The army and allied self-defence fighters and former rebels had "turned hospitals and mosques into military barracks and rocket launchers," the RSF said.

The Sudanese army, which has denied responsibility for civilian deaths, has also used drones in al-Fashir.

REPEATED ATTACKS ON SECOND SHELTER

On October 10-11 another displacement shelter, Dar al-Arqam, located on university grounds that also house a mosque, suffered repeated strikes. The centre's manager, Hashim Bosh, recorded 57 dead including 17 children, among them three babies. 

"They were aiming at the mosque. They attacked right after Friday prayer," he said in a voice note to Reuters, describing the first strike. A second strike, he said, came from a drone that followed people running to another shipping container used as a shelter.

The next morning four more shells hit during dawn prayers, Bosh said. Residents interviewed in footage taken by local activists and verified by Reuters confirmed the attacks.

The footage also showed what appear to be 10 bodies covered in sheets at the site, a child-sized body covered by a small prayer rug, and several bodies, mangled and uncovered, inside the container.

Satellite imagery published by the Yale Humanitarian Research Lab (HRL) on October 16 showed six impact points on Dar al-Arqam's buildings.

BODIES SCATTERED IN THE STREETS

According to HRL, as of October 4 the RSF had extended earthen barriers to almost fully encircle al-Fashir.

As a result, activists warned last week that even ambaz, an animal feed people had resorted to eating, had become unavailable.

Activists from a local network, the al-Fashir Resistance Committee, say on average 30 people a day are dying from violence, hunger, and disease.

So many bodies were scattered in the streets that it was a health risk, according to the Abu Shouk Emergency Response Room, a volunteer network.

Those who spoke to Reuters said they feared being kidnapped, robbed, or killed if they left.

"Al-Fashir is basically lifeless," said a member of the Abu Shouk Emergency Response Room who only gave his first name, Mohamed. "But leaving is even more dangerous than staying."