PSNI Chief Constable Jon Boutcher said the violence endangered lives and risked the ongoing criminal justice process.
He said the PSNI would pursue those responsible and images would be released to identify offenders.
"To those who have been threatened or affected by this violence: we are with you," he added.
He said the PSNI was "critically underfunded" and would be "making arrangements to activate mutual aid resources".
"Our resourcing levels are not just inadequate – they are dangerous," he said.
The police have also said there was no evidence of paramilitary involvement.
Some homes have begun displaying stickers outlining the residents' nationalities. Signs which read "British household" and "Filipino lives here" could be seen on some doors.
Alliance Party assembly member Sian Mulholland told the BBC's Good Morning Ulster programme that there was a heavily pregnant woman in one of the houses set on fire.
"We were able to direct the police to remove that family and get them out of the area to safety, to the police station," she said.
Mulholland said there was "widespread livestreaming on social media of the violence – directing people where to go, how to get around the police barricades".
'Tensions rising' in Ballymena
A clean-up operation is under way, with debris and burning items being cleared from the roads. Scorch marks and melted bins can be seen on the streets.
Democratic Unionist Party (DUP) assembly member Paul Frew told BBC Radio 4's Today programme he feared someone would be killed in the disorder.
Frew said it was "drowning out the strong and sincere sympathies for victims of sexual violence".
He said tensions had been rising for some time in Ballymena and and people were "frightened about illegal immigration".
Police have urged anyone involved in the unrest "to reflect long and hard about their actions".
Northern Ireland Secretary Hilary Benn said there was "no justification" for the rioting.
The MP for North Antrim, Jim Allister, posted on social media: "Tonight's further senseless violence in Ballymena is helping no cause, just destroying our own town and getting young men criminal records. Stop it."
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