The United States is working with Haitian authorities to try to secure the release of 12 adults and five children with a US-based missionary group who were abducted over the weekend by a gang notorious for killings, kidnappings and extortions.

The group was snatched by the 400 Mawozo gang, which controls the Croix-des-Bouquets area east of the Haitian capital Port-au-Prince, police inspector Frantz Champagne told The Associated Press on Sunday. The abduction happened on Saturday in the community of Ganthier, which lies in the gang's area. It had been blamed for the kidnapping of five priests and two nuns earlier this year.

As authorities sought the release of 16 US citizens and one Canadian with the Ohio-based Christian Aid Ministries, local unions and other organizations were expected to launch a strike on Monday to protest Haiti's worsening lack of security.

Haiti, one of the Western Hemisphere's poorest nations, is again struggling with a spike in gang-related kidnappings that had diminished in recent months, after President Jovenel Moise was fatally shot at his private residence on July 7 and a magnitude-7.2 earthquake killed more than 2,200 people in August.

"Everyone is concerned. They're kidnapping from all social classes," Mehu Changeux, president of Haiti's Association of Owners and Drivers, told Magik9 radio station.

He said the work stoppage would continue until the government could guarantee people's safety.

The kidnapping of the missionaries came just days after high-level US officials visited Haiti and promised more resources for Haiti's National Police, including another $15 million to help reduce gang violence, which this year has displaced thousands of Haitians who now live in temporary shelters in increasingly unhygienic conditions.

The US State Department said on Sunday that it was in regular contact with senior Haitian authorities and would continue to work with them and interagency partners.

Christian Aid Ministries said the kidnapped group included seven women, five men and five children, including a 2-year-old. The organization said they were taken while on a trip to visit an orphanage.

Murders, ransoms

Nearly a year ago, Haitian police issued a wanted poster for the alleged leader of the 400 Mawozo gang, Wilson Joseph, on charges including murder, attempted murder, kidnapping, auto theft and the hijacking of trucks carrying goods. He goes by the nickname "Lanmo Sanjou", which means "death doesn't know which day it's coming".

Amid the spike in kidnappings, gangs have demanded ransoms ranging from a couple of hundred dollars to more than $1 million, sometimes killing those they have abducted, according to authorities.

At least 328 kidnappings were reported to Haiti's National Police in the first eight months of this year, compared with a total of 234 for all of 2020, said a report last month by the United Nations Integrated Office in Haiti.

The spike in kidnappings and gang-related violence has forced Haitians to take detours around certain gang-controlled areas while others opt to stay home, which in turn means less money for people like Charles Pierre, a moto taxi driver in Port-au-Prince who has several children to feed.

"People are not going out in the streets," he said. "We cannot find people to transport."

Agencies and Heng Weili in New York contributed to this story.