Floods swamped a handful of cities in southern China’s densely populated Pearl River Delta following record-breaking rains, sparking worries about the region’s defences against bigger deluges induced by extreme weather events.

On Monday, rescuers on boats in China’s flood-hit Guangdong province raced to evacuate trapped residents, carrying some elderly people by piggyback from their homes and deploying helicopters to save villagers caught in landslides.

State media on Monday said four people were killed in riverside cities while a search was underway for 10 others missing. The official Xinhua news agency said three people died in Zhaoqing city while one rescuer died in Shaoguan city. It didn’t say when or how they died.

The province once dubbed the “factory floor of the world” is prone to summer floods. Its defences against disruptive floods were severely tested in June 2022 when Guangdong was pounded by the heaviest downpours in six decades. Hundreds of thousands of people were evacuated.

Since Thursday, Guangdong has been battered by unusually heavy, sustained and widespread rainfall, with powerful storms ushering in an earlier-than-normal start to the province’s annual flooding season in May and June.

In Qingyuan, a relatively small city of about 4 million north of the provincial capital Guangzhou, residents said the flooding over the weekend was not as severe as the 2022 floods, but they were still concerned.

“We’re worried the floods could be worse than two years ago,” said Song Xiaowei, who works at a spare parts factory.

“I’ve friends in Jintan town who have already removed their furniture. The village opposite that has been submerged to the first floor.”

Song said his factory was still operating as usual, but rivers were being monitored in case they spilled over onto roads.

One river in the area rose as much as 7 metres, submerging nearby farmland, he said.

Over the weekend, the Bei river, a tributary of the Pearl river running through Qingyuan, overflowed its banks and submerged some houses and shops.

Rescuers tackled muddy waters, neck-high in some areas, to extract residents including an elderly lady trapped in waist-deep water in an apartment building, videos on social media showed.

Before 2022, it rarely rained as heavily as it does now, and the flood waters were never as high, said Qingyuan resident Lin Xiuzheng, who worked in online retail sales.

Weather events in China have become more intense and unpredictable because of global warming.