ROME — An Eritrean man accused of organizing an extensive people-smuggling network that led to the deaths of hundreds of Africans trying to cross the Mediterranean Sea has been captured in Sudan and extradited to Italy, the authorities said Wednesday.

The arrest, which followed an investigation that involved the Sudanese, Italian and British authorities, was a rare instance in which a person has faced direct criminal charges for the human trafficking that has made the Mediterranean one of the world’s deadliest migration routes.

Officials said the smuggling ring was responsible for the deaths of 359 people when a vessel capsized off the Italian island of Lampedusa in 2013. The authorities said the man styled himself as “the General” — a reference to the reach of his criminal network — and that he had been heard on intercepted telephone calls joking callously about the deaths of migrants who were fleeing violence and desperation.

The Italian authorities identified the man as Medhanie Yehdego Mered, 35, though the information could not be independently confirmed. Mr. Mered, they said, was seized in Khartoum, the capital of Sudan, on May 24, and flown to Rome on Tuesday night.

But after the arrest was reported on Wednesday, an Eritrean activist and journalist who hosts a weekly radio program in Stockholm, as well as an article in The Guardian, raised doubts about the identity of the man in custody.

In a telephone interview, the activist, Meron Estefanos, said she had been following the activities of Mr. Mered since 2010.

“When I saw the news this morning that the most wanted smuggler had been extradited, I was happy,” she said. But after video clips of the man in custody began circulating, she began receiving telephone calls — from refugees who said they had been smuggled by Mr. Mered, and people who said they were friends and relatives of the man who had been extradited. All said that the Italians had the wrong man.

“I hope that the Italians admit that they have the wrong person and that they release the person immediately,” Ms. Estefanos said. “This is absurd.”

Asked about the possibility of a mistake, Britain’s National Crime Agency said in a statement late Thursday night that “we have noted the Guardian’s report. This is a complex multipartner operation, and it is too soon to speculate about these claims.”

“The N.C.A. is confident in its intelligence-gathering process,” the agency said.

Earlier, the crime agency said that the Sudanese police carried out the arrest after the British authorities tracked the suspect to an address in the El Diem area of Khartoum.

“Telephone interceptions gathered by the Italians confirmed Medhanie was organizing regular journeys across the Mediterranean, and was also directly coordinating other people-smugglers responsible for land routes,” the agency said in a statement, using what the Italian authorities said was Mr. Mered’s first name. “During one recorded conversation Medhanie was heard laughing about the fatal overloading of migrant ships.”

The sinking of the boat, a flimsy fishing vessel, off Lampedusa on Oct. 3, 2013, was a signal moment in the migration crisis. While refugees from the Syrian civil war have been among the most prominent faces of the problem, many other migrants from strife-torn countries in sub-Saharan Africa, including Sudan and Eritrea, have traveled to Libya, where there is barely a functioning government. Part of the Italian region of Sicily, Lampedusa, about 70 miles from Tunisia, has been a destination for many African migrants.

The boat was packed with more than 500 people. Of the 155 who survived the shipwreck, around 100 ended up in Sweden.

“This operation is important not only because it struck one of the bosses of a criminal ring that has smuggled thousands of people, but also because it effectively demonstrated international judicial and police cooperation,” Francesco Lo Voi, the chief prosecutor in Palermo, the regional capital, said on Wednesday.

Mr. Lo Voi said that Mr. Mered had been responsible for smuggling thousands of migrants to Italy since 2012, making “enormous profits” without regard for the life-threatening risks taken by the migrants. Like the British authorities, Mr. Lo Voi took note of the phone call in which Mr. Mered was recorded laughing about the overloading of the boats.

A statement from Mr. Lo Voi’s office said Mr. Mered “not only directed the activities in the African continent, but also constantly kept abreast his collaborators in Italy with the boat arrivals, so that migrants could continue traveling to their final destination.”

“The General” is suspected of controlling a large area through his contacts and of personally coordinating smugglers on the land routes in Africa, Italy, the Netherlands and Scandinavian countries.

In several cases, Italian prosecutors said, he paid Libyan officials to free migrants from Libyan jails, then sought to extort compensation from the migrants’ families. In one wiretapped conversation, Mr. Mered boasted that he had paid $40,000 to Libyan jailers to free a group of people.

The migrants were “authorized” to leave for Italy — or to leave Italy for other parts of Europe — only after their relatives made additional payments, prosecutors said. The payments were made in phases: one for the land route through Libya, a second to cover the sea crossing and a final payment if the migrants made it to destinations north, like Germany or Sweden.

“This business had a great economic value,” a prosecutor in Sicily, Maurizio Scalia, said Wednesday in a news conference.

Mr. Mered, the prosecutors said, had boasted that he had bought a house in Eritrea and could receive bank payments in and from any European country, and even in Israel.

He was recorded as saying that he had a brother in the Netherlands, and a wife and son in Sweden and hoped to join her there after stashing enough money from his “accumulated treasure,” prosecutors said.

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© 2016, The New York Times