The Mexican government issued a hurricane watch Monday as Tropical Storm Marco formed over the warm waters of the Gulf of Mexico.

At 8 p.m. ET, Marco had winds of 105 km/h and was centred 128 kilometres east of Veracruz, the U.S. National Hurricane Center reported.

The centre said some strengthening is forecast during the next 24 hours. Winds would need to increase to 119 km/h to make it a Category 1 hurricane.

The watch is in effect for the coastal area from Veracruz north to Cabo Rojo, just south of Tampico.

A tropical storm warning has been extended to cover an area from Cabo Rojo southward to Punta el Lagarto.

Marco is moving west-northwest at 15 km/h. On this course, the storm centre will be near the coast of Mexico sometime Tuesday, forecasters said.

The hurricane centre said Marco is a small tropical cyclone, with storm force winds extending outward up to 45 kilometres from the centre.

Mexico's state-owned oil company, Pemex, began evacuating four offshore oil platforms in the Gulf of Mexico Monday due to Tropical Storm Marco.

Pemex said in a statement it also shut six wells at the Lankahuasa platform and had stopped operations at one gas plant.

Meanwhile, Hurricane Norbert has formed far off Mexico's Pacific coast, the hurricane centre said late Monday.

Norbert is centered 510 kilometers south-southwest of the port city of Manzanillo, and is not expected to threaten land.

With files from Reuters and the Associated Press