Gunfire ripped through residential neighbourhoods of Sudan's capital Khartoum at the start of the Muslim holiday of Eid al Fitr on Friday, after the army deployed on foot for the first time in its almost week-long fight with a paramilitary force.

Soldiers and gunmen from the paramilitary Rapid Support Forces (RSF) shot at each other in the north, west and centre of the city, including during the call for special early morning Eid prayers, witnesses said.

The unabated fighting has killed hundreds and tipped Africa's third largest country - where around a quarter of people already relied on food aid - into a humanitarian disaster.

An international push for a temporary truce to allow civilians to reach safety and visit family over the three day holiday has so far failed. Foreign nations including the United States, Japan, South Korea, Germany and Spain have been unable to evacuate their citizens.

Instead of a ceasefire, the army has entered a new phase, fighting the RSF on the ground, after having stuck largely to air strikes across the capital, with fiercer clashes in central Khartoum, since the power struggle erupted last weekend.

In a statement, the army said it had begun "the gradual cleaning of hotbeds of rebel groups around the capital".

Khartoum resident Mohamed Saber Turaby, 27, had wanted to visit his parents 80km from the city for Eid.

"I'm not lucky. Every time I try to leave the house, there are clashes, he said. "There was shelling last night and now there is presence of army forces on the ground."

Army chief General Abdel Fattah al-Burhan said on Thursday he saw "no other option but the military solution".

Heavy weaponry thudded across Khartoum and its Nile sister cities, together one of Africa's biggest urban areas.

Army troops brandishing semi-automatic weapons were greeted by cheers on one street, a video released by the military on Friday showed. Reuters verified the location of the video, in the north of the city, but could verify when it was filmed.

Gunshots crackled without pause and black smoke drifted above the rooftops into the afternoon.

The World Health Organization said at least 413 people have already been killed and thousands injured in the conflict, with hospitals under attack and up to 20 000 people fleeing into neighbouring Chad.

The United Nations World Food Programme halted its Sudan operation, one of the largest food aid missions in the world, on Saturday after three of its workers were killed.

Thousands of people braved the fighting to flee Khartoum on Friday, witnesses said, moving south to Al Gezira state, or north to River Nile state, with some seeking to go onward to Egypt.

Sudan borders seven countries and sits between Egypt, Saudi Arabia, Ethiopia and Africa's volatile Sahel region. The hostilities risk fanning regional tensions.

The violence was triggered by disagreement over an internationally backed plan to form a new civilian government four years after the fall of autocrat Omar al-Bashir to mass protests, and two years after a military coup.

Both sides accuse the other of thwarting the transition.

DARFUR CASUALTIES

The fighting on Friday undermined efforts by UN Secretary General Antonio Guterres to win a truce, despite a flurry of phone calls to Burhan from the US, Qatari, and Saudi foreign ministers, the Turkish president, and other world leaders on Thursday.

The RSF expressed willingness to allow a lull in the fighting, and condemned the military for what it said was new assaults.

Beyond the capital, the two sides are fighting in the western region of Darfur, where a partial peace deal was signed in 2020 in a long-running conflict that led to international war crimes charges against Bashir.

In El Fasher in North Darfur, a maternity hospital repurposed to treat casualties from fighting was overwhelmed and rapidly running out of supplies, said Cyrus Paye, coordinator for aid group MSF which supports the facility. All other hospitals in the city were closed.

Most of the 279 wounded patients the hospital received since Saturday were civilians hit by stray bullets, many of them children, and 44 have died, he said.

Another doctors' group said at least 26 people were killed and 33 were wounded El-Obeid city, also west of Khartoum, on Thursday. Witnesses there described clashes and widespread looting.

Guterres, speaking to reporters after meeting virtually with the heads of the African Union, the Arab League and other organisations on Thursday, said trapped civilians should be allowed to seek medical treatment, food and other supplies.

Burhan told Al Jazeera he would support a truce on condition it allowed citizens to move freely, which he said the RSF had prevented.