Armed gangs in Haiti opened fire on U.S. Embassy vehicles and a United Nations helicopter this week, an escalation of attacks as criminal groups overwhelm security forces in the country — including an international mission charged with taking on the gangs.

The helicopter was hit in midair by gunfire on Thursday while flying over the capital, Port-au-Prince, a U.N. official said. It was carrying three crew members and 15 passengers.

No one was injured, and the helicopter landed safely, according to the official, Arnaud Royer, the head of the U.N. human rights office in Haiti. The helicopter is used by the U.N.’s World Food Program to deliver humanitarian aid to Haitians, many living in communities cut off by gangs.

On Monday, gangs fired on two U.S. Embassy vehicles traveling in Port-au-Prince. A State Department spokeswoman confirmed that no workers were injured. Officials told The Times that some two dozen embassy employees would be evacuated.

“The United States strongly condemns ongoing gang violence in Port-au-Prince aimed at destabilizing the government,” Brian A. Nichols, assistant secretary of state for Western Hemisphere affairs, said in a statement after the attack on Monday. “Those responsible will be held to account by Haitian and international authorities.”

In an effort to restore order to the gang-ravaged country, a multinational security force was deployed to Haiti in June. The mission, made up so far of about 430 Kenyan, Jamaican, Bahamian and Belizean officers, is meant to act as reinforcement for the outgunned, underfunded and severely underpaid Haitian police.