The toll from Hurricane Agatha climbed to at least ten dead and around 20 missing in southern Mexico, where heavy rains triggered landslides and flooding, local officials said Tuesday.

The storm, the first hurricane of the Pacific season, was the strongest to make landfall along Mexico's Pacific coast in May since record keeping began in 1949, the US National Hurricane Center (NHC) said.

"Right now we're at around 20 people missing, most of them are in the upper mountains," Oaxaca state governor Alejandro Murat told Radio Formula, adding that "ten who lost their lives were unfortunately preliminarily reported by local authorities."

"When Agatha made landfall, the day ended without any loss of human life, but heavy rains that occurred early Tuesday morning caused rivers to burst their banks and landslides," Murat said earlier in the day.

An earlier toll had repored three dead and eight missing.

Two people aged 18 and 21 years old died when part of a hill collapsed in the community of Santa Catarina Xanaguia, the Oaxaca civil protection office said.

Another woman died and her son was injured in a landslide in Llano del Chillar, it said.

Mexico is regularly lashed by tropical storms on both its Pacific and Atlantic coasts, generally between the months of May and November.

The deadliest storm to hit Mexico last year was a Category 3 hurricane called Grace that killed 11 people in the eastern states of Veracruz and Puebla in August.