Fighting erupted on Friday between M23 militiamen and government troops near the eastern DR Congo city of Goma, where a European mercy flight arrived in the afternoon, sources said.
The aid mission is the first in an airlift announced last Saturday by the European Union to help the beleaguered city.
The plane landed on Friday afternoon, carrying 35 metric tons of material, including tents, mattresses and medical equipment.
Standing on the tarmac of Goma airport, EU ambassador to the Democratic Republic of Congo Jean-Marc Chataigner told reporters that another plane would land next week, with others to follow.
The city of over one million people is increasingly threatened by M23 rebels, who have captured swathes of North Kivu province since re-emerging from dormancy in late 2021.
Goma has the Rwandan border to its east and Lake Kivu to its south. The M23 controls much of the territory to the north of the city and is now also encroaching from the west, threatening to cut off all road links to the city.
After a day of relative calm, clashes unfolded early Friday near the village of Murambi, less than 30 kilometres (18 miles) west of Goma, local officials said.
Murambi is the last settlement before the town of Sake, considered the city's last bulwark.
"The population is starting to panic again," Leopold Busanga, a spokesman for civil society groups in Sake.
Fighting was also reported further north, around 70 kms (43 miles) from Goma, an official there said.
The UN's refugee agency (UNHCR) stated on Friday that it was "greatly alarmed" as the conflict has driven hundreds of thousands from their homes.
Some 300,000 in North Kivu fled in February alone, UNHCR said. More than 800,000 people have been displaced in the province since March last year.
Chataigner told reporters that some 600,000 people had come to Goma and its surrounding area in the past several months.
Standing by his side, France's ambassador to the DRC Bruno Aubert said: "What's happening in eastern Congo is intolerable".
The M23, whose name stands for the March 23 Movement, is one of scores of armed groups that roam eastern DR Congo, many of them a legacy of two regional wars that flared at the end of the 20th century.
In 2012, the Tutsi-led group briefly captured Goma before a joint Congolese-UN offensive drove it out.
But fighting erupted again in late 2021 after the M23 accused the Congolese government of ignoring a promise to integrate its fighters into the army.
The rebels then started to conquer large chunks of North Kivu last summer, and have continued advancing despite international pressure to down arms.
The DRC accuses its smaller neighbour Rwanda of supporting the group, something that Kigali denies, and regional countries have deployed a joint force aimed at stabilising the region.
Independent UN experts, the United States and several other western countries also agree that Rwanda is backing the M23.
In recent months, several ceasefires have been attempted, the latest of which was supposed to have taken effect on Tuesday.
All have failed.
A United Nations Security Council delegation arrived in the DRC late Thursday for a three-day visit to assess the situation.
The team is due to meet President Felix Tshisekedi and fly to Goma on Saturday.