A Canadian frigate has departed Halifax to replace a sister ship that is part of a NATO maritime force aiming to reassure eastern European allies that are worried about the crisis in Ukraine.

HMCS Fredericton will take over from HMCS Toronto in the operations in the Mediterranean Sea.

Toronto has been in the area since August, and Fredericton is expected to deploy for a similar six-month period after the ships meet up in Spain.

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Fredericton is the first frigate that's received upgrades through a $4.3-billion modernization program to participate in the NATO operation.

The ship has a new combat management system, refurbished radar systems, upgraded communications and a more recent generation of missiles.

It departed Tuesday with a crew of about 250 people and a CH-124 Sea King helicopter and air attachment on board.