Christchurch, New Zealand ? A powerful earthquake struck New Zealand’s already-bruised city of Christchurch today, collapsing buildings, burying vehicles under debris and sending rescuers scrambling to help trapped people amid reports of multiple deaths.

The 6.3-magnitude quake hit the country’s second-biggest city on a busy weekday afternoon and closer to downtown than a major quake that damaged Christchurch last September but caused no deaths when it struck before dawn on a weekend.

Police said there were reports of multiple fatalities from the latest temblor in the city of 350,000, while Prime Minister John Key told Parliament it was still too soon to confirm the deaths.

The quake destroyed the spire of the iconic stone Christchurch Cathedral, which toppled into a central city square, and police said there was a report of two buses crushed under falling buildings.

Video footage showed some multistory buildings collapsed in on themselves, and others with walls that had collapsed into the streets, strewn with bricks and shattered concrete. Sidewalks and roads were cracked and split, and thousands of dazed, screaming and crying residents wandered through the streets as sirens blared. Groups of people helped victims clutching bleedings wounds, and others were carried to private vehicles in makeshift stretchers fashioned from rugs or bits of debris.

Christchurch Mayor Bob Parker declared a state of emergency and ordered people to evacuate the city center. Troops were deployed to help people get out and to throw up a security cordon around the stricken area, said Deputy Prime Minister Bill English.

“Make no mistake — this is going to be a very black day for this shaken city,” Parker said when asked about possible deaths.