The last 72 hours has seen some of the worst levels of violence in Bangui, the capital of the Central African Republic (CAR), in over a year, according to Doctors without Borders (MSF), the medical charity.
The violence has overwhelmed medical facilities and crippled humanitarian work, the charity says.
Emmanuel Lampaert, head of operations at MSF in Bangui, told Al Jazeera over the phone on Tuesday that up to 150 people had been wounded in clashes between communities in the city since Saturday.
"This is the worst violence we have seen in a year, and this time the medical consequences are higher," he said.
"Our teams are also finding it difficult to move to areas with needs as the barriers to assist have become far more visible."
Lampaert's comments come as reports emerged of a massive jail-break in Bangui.
About 500 prisoners, mostly anti-Balaka (anti-machete) fighters, are said to have escaped in a move that is likely to destabilise the city further.
Bangui has seen a wave of violence since the reported murder of a Muslim taxi driver on Saturday.
The decapitated young man was found outside a mosque.
Members of the Muslim community then attacked a Christian neighbourhood in a set of clashes that left 42 people dead and destroyed entire districts, reports said.
Reports of looting
The violence is threatening to spin out of control, with reports emerging of international nongovernmental organisations' offices being attacked and looted on Tuesday.
Dalia al-Achi, spokesperson for the UN refugee agency, told Al Jazeera that one member of its staff was attacked on Monday evening, and that UNHCR was evaluating the safety of their staff, even though humanitarian needs were escalating.
The violence against humanitarian agencies is bound to affect their ability to assist vulnerable communities, already hard hit by a sense of insecurity across the country.
Achi said that since Saturday alone, 27,400 people had been displaced by the resurgent violence.
The International Crisis Group (ICG) released a statement on Tuesday urging authorities to delay elections in the country, currently scheduled for October 18.
Speaking from Paris, Thierry Vircoulon, Central Africa Project director for the ICG, told Al Jazeera it was clear the uptick in violence was linked to "the lack of authority in Bangui", with both the country's president and head of the UN peacekeeping force MINUSCA away in New York for the UN General Assembly .
Acting President Catherine Samba-Panza reportedly left New York on Monday to return home as news broke of heavy clashes in the capital.
"The next week is going to be very critical for CAR [... ] there will be a need to show authority and a will to clamp down on the violence," Vircoulon said.
'Deep concern'
Nick Birnback, a spokesman for the peacekeeping office at the UN headquarters, said MINUSCA was patrolling "and doing everything it can to stabilise the situation".
The UN Security Council also issued a statement on Monday expressing "deep concern about the upsurge of violence" and repeated its demand that all militias and non-state armed groups immediately lay down their arms.
CAR has been hit hard by communal violence since the coup in March 2013, when Muslim-led Seleka rebels took Bangui, and meted out large-scale revenge against the Christian community.
The reprisal from vigilante Christian groups resulted in the displacement of hundreds of thousands as the country became locked in a cycle of violence.
The past few months have seen a sizable reduction in violence, with Bangui being protected by UN peacekeeping forces.
While the violence over the past three days demonstrates the fragility of peace in the capital, humanitarian agencies and regional experts say that rural areas are still at the mercy of armed groups.