Allan Potter, 50, and Bradley Summers, 32, made an appearance in provincial court on Saturday after they were arrested in downtown St. John's.
Police made the arrest on Friday afternoon in a joint investigation by the Royal Newfoundland Constabulary and the RCMP into outlaw motorcycle gangs.
The men are jointly charged with six counts of assault and four counts of uttering threats.
There were multiple victims in the attacks.
Potter and Summers lived in a house on Hamilton Avenue that was firebombed on May 31 — the same day as a drive-by shooting on Dauntless Street.
RNC said at the time that the two incidents were connected and that there was a biker gang connection.
On Friday, police said the investigation was ongoing and would not comment on whether or not more arrests were coming.
The two men will appear in court on Tuesday for a bail hearing.