Tropical Storm Ernesto strengthened into a hurricane and headed toward landfall near Mexico's border with Belize Tuesday, bringing the threat of powerful winds and torrential rains to the Caribbean coast.

The U.S. National Hurricane Center said Ernesto had winds of 129 km/h and was located about 298 kilometres east of Chetumal, Mexico.

Soldiers and police were moving 600 residents from the fishing village of Punta Allen in Mexico's Quintana Roo state, where authorities opened emergency shelters and began preparing for the evacuation of other low-lying coastal settlements.

The heart of the storm was expected to hit south of Cancun and the Riviera Maya, though strong rain and winds were likely there, and officials also prepared shelters there as a precaution.

The storm that entered the Caribbean on Saturday was driving through the sea parallel to the Honduran coast, though officials there said the threat had passed without any damage or injuries.

Nicaragua had evacuated hundreds of people living along the coast, but it too apparently was spared significant damage.

Forecasters said that after moving ashore near the Belize-Mexico border early Wednesday the storm was expected to pass near the jungle Mayan ruins of Calakmul and eventually enter the southern Gulf of Mexico and hit the Gulf coast near the city of Veracruz.

Hurricane warnings were posted for the entire coast of Belize and the southern half of Mexico's Caribbean Yucatan coast.

Tropical storm warnings were issued for the northern part of the Yucatan coast up to Cancun.

Mexican authorities warned of possible flooding in an area where swollen rivers in the past have swept away houses, livestock and people and collapsed mountainsides. In a landslide last year, 31 people were buried in the Chiapas state town of Juan del Grijalva.

Meanwhile, Tropical Storm Gilma formed in the Pacific Ocean, 1,000 kilometres west of Mazanillo, Mexico, with winds of 64 km/h. The storm was not expected to threaten land.