Three alleged members of a radical Dutch Islamic group were arrested in June and deported to the Netherlands because police feared they were planning an attack on then-Prime Minister Jose Barroso, a former top Portuguese police official said in comments published Monday.

The government in the Netherlands confirmed that three men arrested June 11 in Porto, Portugal — the site of the European Championship soccer tournament — are alleged members of a group referred to by Dutch intelligence as the "Hofstad Network (search)," which has been linked to the Nov. 2 killing of filmmaker Theo van Gogh (search).

The suspects, whose names have not been confirmed by authorities in either country, are believed to have been arrested in a sweep after Van Gogh was shot and stabbed in Amsterdam.

The suspects in Portugal drove a car registered to Mohammed Bouyeri (search), who has been arrested in connection with the killing of Van Gogh, according to former Portugal national police chief Adelino Salvado, who spoke to the daily newspaper Diario de Noticias.

Bouyeri, 26, a dual Dutch-Moroccan citizen, was arrested minutes after Van Gogh's murder with a note in his pocket saying he planned to die in the name of jihad, or Islamic holy war.

The newspaper report identified one of three men detained in June as El Fahtni Noreddine. Dutch media identified one of 13 men arrested last week in connection with Van Gogh's murder as Nouredine El F., who shared an apartment with Bouyeri.

Police feared the men were planning an attack during the soccer tournament, Salvado said. About 1 million fans attended games at the three-week competition involving 16 national teams.

Police officials were not immediately available Monday for comment.

Salvado said "foreign intelligence services" wanted to keep the men under surveillance but Portuguese police feared they were preparing an attack on then-Prime Minister Jose Manuel Barroso (search) and foreign dignitaries among the 700 people due to attend a gala dinner in Porto on June 11, the eve of the soccer tournament.

Dutch officials said the three were deported back to the Netherlands on June 16 and June 21 by Portuguese authorities because there wasn't enough evidence to hold them.

Salvado said he "couldn't take risks. Everything indicated they were preparing an attack," according to the newspaper.

Van Gogh, whose last film was critical of how women are treated under Islam, was a distant relative of Dutch painter Vincent Van Gogh. The slaying has triggered retaliatory vandalism against some mosques and Islamic schools in the Netherlands.