The United States is organizing a charter flight to evacuate its citizens from Haiti, the US embassy said on Saturday, after weeks of gang violence that has paralyzed the Caribbean country.

The emergency flight will depart from Cap-Haitien, Haiti's second-largest city, as the main airport in capital Port-au-Prince remains shut amid the unrest.

"We are arranging a charter flight for U.S. citizens from Cap-Haitien to the United States, assuming the security situation in Cap-Haitien remains stable," the US embassy in Haiti said in a security alert posted on its website.

The embassy said the airport in Cap-Haitien is open "periodically" for departing flights.

No date for the evacuation has been announced and it is unclear how many Americans will be able to take the flight.

The embassy warned that the 120-mile (200-kilometer) overland journey from Port-au-Prince to Cap-Haitien is "dangerous," telling its citizens to consider the flight "only if you believe you can reach Cap-Haitien airport safely."

The United States said last Sunday it had airlifted non-essential American staff from its embassy in Port-au-Prince and brought in additional personnel to boost security at the compound.

Several other countries and the European Union have evacuated diplomatic personnel due to the crisis.

The United Nations also said it was evacuating non-essential staff.

The UN mission in Haiti announced Wednesday it would launch an "airbridge" from neighboring Dominican Republic to facilitate the movement of aid into the country.

Haiti has been convulsed for the last two weeks by a gang uprising, with the well-armed groups aiming to topple Prime Minister Ariel Henry, an unpopular and unelected leader.

Henry agreed to step aside after an emergency meeting Monday that brought together parties including the US, UN and Caribbean representatives, yielding a blueprint for Haitians to form a governing Transitional Presidential Council until elections can be held.

Earlier on Saturday, authorities said police seized firearms and cleared roadblocks in a Port-au-Prince neighborhood controlled by notorious gang leader Jimmy "Barbecue" Cherizier, in an operation that left several criminals dead.