BRUSSELS—European police have dismantled a criminal ring that in less than a year had smuggled hundreds of migrants out of Hungary to Austria and Germany, law-enforcement officials said Monday.

The arrests show the sophistication of smuggling operations in Europe. With new restrictions on movement across borders and the political will to accept new immigrants faltering, it has become more difficult for migrants and refugees to reach their preferred destinations. The main migrant trail into Europe, from Greece through the Balkans, has been largely sealed through European Union efforts.

The suspected ringleader, a 44-year Syrian national, along with six other accomplices of Russian origin, were arrested late last week in Austria, Franz Ruf, head of the Salzburg police, said Monday at a news conference.

Another suspect was arrested in Hungary, in a joint operation coordinated by the European Union's police agency Europol, the agency said.

Police didn't reveal the identities of any of the persons arrested.

Authorities said the smuggling group was comprised of at least 25 Russian nationals of Chechen origin residing in Austria. The Chechens, according to authorities, were dispatched to Hungary to recruit migrants in the refugee camps.

The Syrian national who acted as the ringleader, working mostly out of a Budapest hotel, was in permanent contact with the recruiters and drivers, Europol said.

According to Austrian officials, drivers often rode in convoys. The smugglers used cars driving ahead of the rest of the convoy to make sure that the road was clear of police patrols. They often changed routes, sometimes traveling via Slovakia, instead of going straight from Hungary to Austria, to avoid detection.

The smuggled migrants were of Afghan, Iranian, Iraqi and Syrian nationality and were registered asylum seekers in Hungary who left the camps without permission, said Europol.

The smugglers were charging around €300 per person for a trip from Hungary to Vienna and €700 to €800 from Hungary to Germany, Austrian police said. The crime network is charged with having smuggled at least 200 people, but Austrian police estimate the actual number may be over 1,000.

According to Austrian police, the investigation into the network started on Sept. 5, 2015, when a Polish smuggler and 17 migrants were arrested on the parking lot of a supermarket in Salzburg. Three other cars managed to get away.

The three alleged fugitive drivers were arrested in May in Poland, along with a 39-year old Polish citizen who is suspected of having acted as a link to the Chechen organization. The 39-year old was looking for drivers in Poland for "refugee transports" on the Budapest-Vienna route, offering €700 per trip, Austrian police said.

The smuggling network used coded communication, according to phone intercepts. The smugglers called adult migrants "pallets" while "smaller pallets" meant children and "papers" meant bank notes. They often spoke of "meat transports" in reference to the persons to be smuggled, authorities said.

In all, authorities said, 17 people have been arrested in connection with the smuggling ring since last September. The accused are facing charges of people smuggling, participation in an organized criminal group, organized criminality, illegal possession of weapons and documents forgery.

Write to Valentina Pop at valentina.pop@wsj.com

(END) Dow Jones Newswires

July 25, 2016 14:15 ET (18:15 GMT)