Tuguegarao – Typhoon Mangkhut rocked Hong Kong en route to mainland China on Sunday, lashing its coastline and sending skyscrapers swaying, after killing at least 30 people in the Philippines and ripping a swathe of destruction through its agricultural heartland.The world's biggest storm this year left large expanses in the north of the Philippines' main island of Luzon underwater as fierce winds tore trees from the ground and rains unleashed dozens of landslides.In Hong Kong, weather authorities issued their maximum alert for the storm, which rocked the city with violent gusts that have reportedly reached 232km/h.As the storm passed south of Hong Kong, trees were snapped in half and roads blocked, while some windows in tower blocks were smashed and some skyscrapers swayed, as they are designed to do in intense gales.Counting the costThe Philippines was just beginning to count the cost of the typhoon, but police confirmed at least 30 were killed when it smashed into northern Luzon on Saturday.In the town of Baggao, the storm demolished houses, tore off roofs and downed power lines. Some roads were cut off by landslides and many remained submerged.Farms across northern Luzon, which produces a large portion of the nation's rice and corn, were sitting under muddy floodwaters, their crops ruined just a month before harvest."We're already poor and then this happened to us. We have lost hope," 40-year-old Mary Anne Baril, whose corn and rice crops were spoiled, told AFP."We have no other means to survive," she said tearfully.Nearly five million people, almost a quarter of whom live on just a few dollars per day, live in the storm's path.'High threat' to Hong KongAn average of 20 typhoons and storms lash the Philippines each year, killing hundreds of people.The latest victims were mostly people who died in landslides, including a family of four. In addition to the 30 killed in the Philippines, a woman was swept out to sea in Taiwan.The country's deadliest storm on record is Super Typhoon Haiyan, which left more than 7 350 people dead or missing across the central Philippines in November 2013.In Hong Kong's famous Victoria Harbour and fishing villages, water levels could surge by up to four metres, authorities said earlier. Hundreds of residents were evacuated to storm shelters as the observatory forecast severe flooding for low-lying areas.Shop windows were taped up and the normally traffic-clogged streets were deserted.The government warned people to stay indoors but some were strolling in parks or along the waterfront on Sunday morning."I went running this morning. I love fresh air and there's no one on the streets, no cars. On normal days we can't see this," said Hao Chen, 28, who lives in the neighbourhood of Tin Hau, on Hong Kong Island.Extra precautions, preparationsResident Antony Kwok in the fishing village of Tai O said flood defences and ladders had been set up to protect those who live in the area's stilt houses as waters began to rise.Almost all flights in and out of Hong Kong were cancelled.In the neighbouring gambling enclave of Macau, all 42 casinos shut on Saturday night and businesses were shuttered on Sunday morning, some boarded up and protected by piles of sandbags.Streets in parts of Macau were underwater as a storm surge sent water gushing from the harbour into the city.The government and casinos are taking extra precautions after Macau was battered by Typhoon Hato last year, which left 12 dead.Preparations were in high gear on China's southern coast, including in Yangjiang, which is not often hit by major typhoons and where the city's 2.4 million people were bracing for a direct hit.Further down the coast preparations were also underway in Zhanjiang, where some villagers feared for the worst."I couldn't sleep last night, I saw the typhoon on television and how intense it was," said 55-year-old Chan Yau Lok.