Another youth has been charged with the murder of Ballymena teenager Michael McIlveen.
The 15-year-old, who cannot be named, was charged yesterday at Coleraine Magistrates Court, Co Derry, along with a 16-year-old who is facing a charge of affray.
Opposing bail, Supt Terry Shevlin said: "If this young man was in the Ballymena area it would be extremely difficult, maybe nigh on impossible, to guarantee his safety."
The situation in the town was "very grave" and the PSNI fear an outbreak of street disorder, he said.
The court heard that when charged with affray, the 16-year-old boy replied "no".
Resident Magistrate Richard Wilson refused to grant bail to the 16-year-old, citing safety and other reasons.
The accused boy was remanded in custody to appear at Ballymena Magistrates Court on June 8th.
The 15-year-old replied "not guilty" to both charges and was also remanded in custody to June 8th, along with five other teenagers who were last week charged with murder.
Supt Shevlin said police had already issued 12 notices of threats to those allegedly involved in the murder and to others, including one witness.
Tensions in Ballymena were "very, very high," he said. "There are fears of retaliation from republicans and fears of retaliation on that from loyalist elements." People were being intimidated via the internet, he added.
The youths will appear by video link with the co-accused in court next month.