Multiple nations have scrambled to evacuate embassy staff and citizens by road, air and sea from Sudan, where fighting between the army and paramilitaries has killed hundreds and led to acute shortages of water, food, medicines and fuel.

Rescue operations intensified in recent days as a 72-hour ceasefire took effect on Tuesday.

"Recently, the security situation in Sudan has continued to deteriorate," Chinese defence ministry spokesman Tan Kefei said.

The navy was deployed on Wednesday, he added, "in order to protect the lives and property of Chinese people in Sudan".

On Monday, China said it had safely evacuated a first group of citizens, estimating about 1,500 of its nationals were in Sudan.

Tan did not specify the number of vessels involved.

China says it is Sudan's largest trading partner, with more than 130 companies investing there as of mid-2022.

Some 800 Chinese citizens would be evacuated from Sudan by sea from April 25 to 27, foreign ministry spokeswoman Mao Ning said Wednesday.

More than 300 other people have crossed over to countries bordering Sudan by land, she added.

The fighting has killed at least 512 people and wounded more than 4,000, according to Sudan's health ministry, and reduced some districts of greater Khartoum to ruins.

UN agencies reported Sudanese civilians "fleeing areas affected by fighting, including to Chad, Egypt and South Sudan".

With the capital Khartoum's international airport disabled after battles that damaged many aircraft, many foreigners have been airlifted out from smaller airstrips.

Other evacuations were taking place from Port Sudan, an 850-kilometre (530-mile) drive from Khartoum.

An Indonesian military plane flew 110 Indonesian nationals from Port Sudan to the Saudi city of Jeddah on Wednesday, the foreign ministry tweeted Thursday.

It brought the total number of Indonesians evacuated from Sudan since the outbreak of conflict to 667.