Haitian gangs are ramping up attacks on areas they do not yet control, the head of the United Nation's Integrated Office in Haiti (BINUH) warned on Tuesday, as the US Embassy said two of its armoured vehicles were attacked on Monday.
The Embassy added there were no reports of injuries.
"The situation in Haiti has regrettably worsened," Maria Isabel Salvador said in a briefing to the UN Security Council, which over a year ago ratified the deployment of an international security force to help police restore order.
Just a fraction of over 3,000 troops pledged by a handful of countries have so far arrived. Funding has also lagged, and an alliance of well-equipped armed gangs known as Viv Ansanm has expanded across the capital and into surrounding regions.
Salvador pointed to mounting attacks over the past week around the capital, its suburbs, farming region and the city famed for the creation of the Haitian flag, where residents have been under an extended siege and pleading for more security reinforcements.
The spread of violence from land and sea, she said, is "spreading terror and fear, overwhelming the national security apparatus."
The international mission, she added, remains "critically under-resourced, which could impact deployment and impede it from carrying out its tasks" in support of the national police.
She also warned of rising tensions between the country's dual executive, headed by the prime minister and presidential council respectively, which are further eroding public trust in the government.
More than 4,200 people have fled their homes in fresh attacks around the capital since last Thursday, according to U.N. estimates, most of these taking refuge in makeshift camps in schools, churches and health centers.
National police has said it is deploying to some areas where the fighting intensified this week, while Prime Minister Garry Conille said on Monday he had immediately recalled several hundred police and soldiers from VIP protection briefs so they can be sent into combat zones.
The conflict has pushed some 700,000 people from their homes and battered the country's food supplies, where over 5 million people are estimated to be going hungry and thousands are facing famine conditions.

Nepal flood losses estimated at $2.56 billion, official says
US investigates deadly strike on Iranian wedding
Nepal to rebuild early-warning system on China border after deadly flood, sources say
US House passes bill to crack down on university boycotts of Israel
Kuwait air defences deal with Iranian missile, drone attacks
Spain's PM Sanchez says no evidence Morocco orchestrated Ceuta border surge
Two Palestinian teens killed in West Bank raid by Israeli settlers, army
Latest Indonesian free meal poisoning outbreaks affect 800, lawmaker says
