Mauritius grounded flights and shut its stock exchange as tropical cyclone Freddy approached the island across the Indian Ocean on Monday, while emergency teams braced for heavy rains, floods and landslides in four regions on Madagascar.
The cyclone, packing gusts of up to 120 km per hour (75 miles per hour), posed a "direct threat" to Mauritius, its weather service said.
"As Freddy approaches ... [a] storm surge is likely to cause coastal inundation in risk areas. It is, therefore, strictly advised not to go at sea," the service's bulletin said.
The cyclone could pass as close as 120 km (75 miles) to the north-northwest of the island late in the afternoon, the service said.
Authorities on the island of Madagascar - about 1,130 km west of Mauritius towards the coast of Africa — said they were expecting a direct hit by Tuesday evening, between Mahanoro in the east and Manakara in south east.
"Torrential rains... very high to enormous seas... and a significant risk of coastal flooding are particularly to be feared in the localities around the point of impact," Madagascar's weather service said.
The government's disaster management office was sending tents, ropes and chainsaws and other supplies to four districts most likely to be affected, officials added.
The Indian Ocean islands and Mozambique on Africa's coast have been hit by a string of deadly storms and cyclones that have forced thousands to flee, destroyed buildings and ruined crops.
In January, tropical storm Cheneso killed 33 people in Madagascar.
