Bertha gathering strength

The heart of Tropical Storm Bertha knocked out power to thousands in Bermuda before churning past the tiny British enclave and heading out over open ocean, where it was expected to strengthen into a hurricane.

The streets of Hamilton are empty and all ferries and flights have been cancelled. The tropical system has flooded roads and downed utility poles, leaving up to 4,000 without electricity but there are no immediate reports of injuries.