A strong 6.0 magnitude earthquake struck close to New Zealand's quake-hit Christchurch today, following a series of earlier tremors which rocked the city. The US Geological Survey said the quake struck at 0220 GMT at a depth of nine kilometres and some 14 kilometres from the country's second largest city. The latest quake follows a string of tremors early today, including one of magnitude 5.2 which reportedly caused building damage in the stricken city. Police said they had received some reports of damage in the city, including flooding, but they were not aware of any injuries. The Christchurch Press reported a building had collapsed, with some people believed to be trapped inside. Christchurch is still recovering from a 6.3-magnitude quake in February which devastated the city centre and killed 181 people.