The U.N. Humanitarian Air Service will restart flights within Haiti on Wednesday, according to a statement from the U.N. World Food Program, which manages the service.

The U.N. paused flights to Haiti's capital last Tuesday, a day after gangs struck three commercial planes with gunfire, prompting the U.S. aviation regulator to ban U.S. airlines from flying to the conflict-ravaged Caribbean nation for 30 days.

"UNHAS provides passenger and light cargo transport in Haiti for the entire humanitarian community, including local and international NGOs," WFP said in a statement, adding that the suspension had not affected food supplies.

Haiti's government helicopter also resumed services Monday, transporting three new government ministers. A cabinet shake-up last week resulted in the ouster of the prime minister and the replacement of many of his top ministers.

Even as the flights restarted, armed violence continued in parts of Port-au-Prince, such as Lower Delmas.

The majority of Port-au-Prince is under the control of armed gangs who have been making gains in recent weeks while a long-delayed, partly deployed U.N.-backed mission to reclaim territories and ensure aid deliveries continues to be stalled.

On Sunday, the U.N.'s International Organization for Migration estimated that more than 20,000 people had been displaced across the capital in just four days, marking the largest mass displacement in over a year.

"The isolation of Port-au-Prince is amplifying an already dire humanitarian situation," the IOM Haiti chief, Gregoire Goodstein, said in a statement, adding that only 20% of the capital was accessible to humanitarian workers.

"Our ability to deliver aid is stretched to its limits. Without immediate international support, the suffering will worsen exponentially," he said.

UNICEF Haiti chief Geeta Narayan said over half of the 20,000 displaced were children, who were facing the "compounded impacts of malnutrition, cholera outbreaks, severe psychological distress and, all too often, tragic loss of life."

The IOM estimated that as of early September over 700,000 people had been internally displaced in the country, while the IPC, a benchmark index of food insecurity, has reported worsening shortages with 6,000 people facing famine-level hunger.