Three suspects in a 2009 double murder in a Tel Aviv gay youth centre appeared in court on Thursday, a day before the beachfront city's annual pride parade, police said.
A fourth man arrested overnight was believed to have information on the case but was not considered a direct suspect, police spokesman Micky Rosenfeld told AFP.
Media described the man as a prominent member of the gay community and quoted his lawyer Ran Alon as saying that his client had no involvement with the case.
Public radio said the three main suspects were led into court manacled to police officers, protesting their innocence, while one aimed a stream of curses at reporters.
Rosenfeld said that police asked for the three to be remanded in custody for 15 days and the fourth man for seven days.
The radio said that the three were also accused of several offences unrelated to the shooting, suggesting a criminal past.
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Most details of the case have been subject to a court-imposed gag order, but press reports said the suspects were all Jewish, aged between 20 and 40, and came from the Tel Aviv suburb of Pardes Katz.
Police sources quoted by the media said the motive appeared to be revenge rather than a hate crime specifically targeting homosexuals.
Liz Trubeshi, 16, and Nir Katz, 26, were killed and 15 others wounded when a masked, black-clad gunman opened fire on a group of young people at the entrance to the youth centre on August 1, 2009.
Survivor Chen Langer, who still has a bullet lodged in his right leg, said the bereaved and disabled were a long way from obtaining closure.
"It will not cure anyone from their terrible feelings, the serious injuries, we shall not recover even after they've caught them. It shocked us all, as a community," he told public radio.
The four-year investigation has reportedly been one of the most extensive and expensive in Israeli police history.
The Haaretz website said the breakthrough came when police found a pistol that they suspect was the murder weapon.