New Zealand on Thursday marked the seventh anniversary of an earthquake that devastated the South Island city of Christchurch in 2011, killing 185 people and injuring thousands.

Of the victims, 115 died in the six-story Canterbury Television building — which collapsed in the 6.3 magnitude temblor — including 28 Japanese students who were studying English at the King's Education language school on the building's fourth floor.

Speaking at a memorial service at the Canterbury Earthquake National Memorial beside Christchurch's Avon River, Prime Minister Jacinda Ardern said the whole of New Zealand is "just as behind Christchurch as they were seven years ago."