Japan is preparing to evacuate its nationals from Sudan, the government said Wednesday, the first nation to publicly announce plans to pull its citizens from the conflict-hit country.

Violence between the Sudanese army and paramilitaries has killed around 200 people since a weeks-long power struggle erupted into deadly battles on Saturday.

The intense conflict has seen air strikes, tanks on the streets, artillery fire and heavy gunfire in crowded neighbourhoods in the capital Khartoum and other cities.

Around 60 Japanese nationals are in Sudan, including embassy staff, top government spokesman Hirokazu Matsuno said.

The defence ministry has begun the "necessary preparations" for evacuations, he told an emergency press conference.

"As the security situation there is worsening, the government is doing its utmost to secure the safety of Japanese expatriates," Matsuno said.

Other nations have urged their citizens in Sudan to provide their names and contact details to their embassies.

The US embassy in Khartoum has started gathering citizens' personal details while urging them to remain indoors and stay away from windows.

"Due to the uncertain security situation in Khartoum and closure of the airport, there are no plans for (a) US government-coordinated evacuation," the embassy tweeted.

International calls are mounting for an end to hostilities in the African country, with G7 foreign ministers on Tuesday urging an immediate ceasefire between the warring forces.

The sides are led by two generals who seized power in a 2021 coup: Sudan's army chief and his deputy, who commands the powerful paramilitary Rapid Support Forces.