The DR Congo army and M23 fighters clashed outside Goma on Friday as the UK, US and France urged citizens to leave the main city in the country’s volatile east, warning the situation could deteriorate rapidly.

Since peace talks failed, the militia group backed by Rwandan troops has gained swathes of territory in mineral-rich eastern Democratic Republic of Congo in recent weeks, triggering a humanitarian crisis and ringing the provincial capital, which is home to a million people.

US, British and French nationals were urged to leave Goma while airports and borders were still open, in online statements or in messages sent directly by email or text.

With fighting intensifying, the United Nations mission in DRC, MONUSCO, said Friday that its peacekeepers were fighting against the M23.

MONUSCO’s Quick Reaction Forces have “been actively engaged in intense combat”, the UN said in a statement, adding that “over the past 48 hours MONUSCO heavy artillery fire carried out fire missions against M23 positions”.

It warned the raging conflict in the North Kivu province had displaced over 400,000 people this year and could spark a regional war.

The UN Security Council will hold an emergency meeting on Monday to discuss the escalating crisis, a spokesperson said Friday evening.

UN chief Antonio Guterres was “alarmed by the resumption of hostilities”, his spokesman said in a statement.

Civilians have been fleeing the fighting since Thursday, travelling on foot to the centre of Goma.

Goma is at the epicentre of the violence that has rocked eastern DRC for 30 years.

The M23 – March 23 Movement – briefly occupied the city at the end of 2012. But the Congolese army, with the support of MONUSCO and diplomatic pressure from the international community on Rwanda, recaptured the city shortly after.

Diplomatic efforts to resolve the crisis have so fair failed.