PORT-AU-PRINCE, Haiti—Hurricane Gustav dumped torrential rains across southern Haiti on Tuesday, killing at least one man and threatening crops amid protests over high food prices. Global fuel futures soared on fears Gustav could move into the Gulf of Mexico as an “extremely dangerous” storm.

Trees toppled as the storm lingered for hours over Haiti’s poor, deforested southern peninsula, and water levels were rising in banana, bean and vegetable fields. One man was killed in a landslide in the mountain town of Benet, civil protection director Marie Alta Jean-Baptiste told Radio Metropole.

“If the rain continues, we’ll be flooded,” U.N. food consultant Jean Gardy said from the southeastern town of Marigot.

Hundreds of people in coastal Les Cayes ignored government warnings to seek shelter, instead throwing rocks to protest the high cost of living in the Western Hemisphere’s poorest country. Witnesses said U.N. peacekeepers used tear gas to disperse the crowd.

Haiti is a tinderbox because of soaring food prices, which in April led to deadly protests and the ouster of the nation’s prime minister. It was difficult to ascertain the extent of the damage to the nation’s crops on Tuesday because of Haiti’s poor infrastructure and faulty communications.

Oil prices shot up $5 a barrel Tuesday after the National Hurricane Center predicted Gustav could enter the gulf as a major hurricane this weekend. Prices of futures in natural gas, heating oil and gasoline also rose.

If Gustav continues on its path, it could drive up U.S. gasoline prices by 10 cents a gallon ahead of Labor Day weekend, predicted James Cordier, president of Tampa, Florida-based Liberty Trading Group and OptionSellers.com.

“Most indications are that Gustav will be an extremely dangerous hurricane in the northwestern Caribbean Sea in a few days,” the Miami-based hurricane center said.

Gustav roared ashore Tuesday afternoon near the city of Jacmel with top sustained winds near 90 mph (145 kph). Heavy rains pelted the area as winds bent palm trees and kicked up surf along waterfronts of dilapidated wooden buildings.

Patrice Tallyrand, 43, fled with his family to a friend’s home after Gustav knocked down four trees in their back yard in the southern town of Kabik.

“We had to leave the house before it got worse,” he said.