PARIS — Belgian police raided nine homes and arrested 10 people in Brussels as part of an investigation into an Islamic State recruitment network, a spokesman for the federal prosecutor’s office said Tuesday.

Three of the 10 were charged with terrorism-related offenses, while the rest were questioned and released without charge, the prosecutor’s office said Tuesday evening.

The arrests were made in the Brussels neighborhoods of Etterbeek, Koekelberg, Molenbeek, and Schaerbeek. Molenbeek was a base for several men involved in the Paris terrorist attacks of Nov. 13 that killed 130 people, and dozens of people have been arrested in Molenbeek in the past three months as the authorities investigate that assault.But the spokesman, Thierry Werts, said the recruitment network targeted in the raids was not directly connected to the Paris attacks.

“The majority of the persons arrested are suspected of having sent people to Syria,’’ Werts said. “Some of them have gone to Syria themselves to fight under ISIS and have returned.’’

During the raids, cellphones, computers, and other hardware were seized for examination, but no weapons or explosives were found, he said.

Molenbeek has become the focus of intense scrutiny since the Belgian government announced an antiterrorism plan this month and assigned hundreds of additional police officers to monitor neighborhoods with large immigrant populations and to crack down on radical activity and the trafficking of arms, drugs, and people.

The investigation is being carried out by a judge from the city of Liège who specializes in terrorism. The three suspects who were charged are men between the ages of 20 and 35 who live in Brussels, prosecutors said; one is a French citizen, and the others are Belgian. They were identified in the statement only by given names and initials. The network they are suspected of being part of is active in and around Molenbeek.

One of the attackers in the 2004 train bombing in Madrid lived in Molenbeek, as did a man accused of shooting four people dead at Brussels’ Jewish Museum in May 2014. In January 2015, Belgian police killed two men from the neighborhood who they suspected were plotting to assassinate police officers in the town of Verviers. The gunman who tried to kill passengers on a high-speed train between Amsterdam and Paris in August 2015 also lived in Molenbeek.