Heavy rains and winds lashed parts of Mozambique on Saturday as Tropical Cyclone Freddy hit the country for the second time in two weeks, authorities and aid agencies said.

Satellite images showed Freddy, which is on track to become the longest-lasting cyclone on record, made its second landfall near the eastern seaport of Quelimane at around 10:00 pm (2000 GMT).

"Freddy made landfall in Mozambique in Quelimane district, Zambezia province, as a tropical cyclone," the UN Office for the Coordination of Humanitarian Affairs (OCHA) said in a statement.

A high risk of flooding was forecast for Zambezia and neighbouring Nampula province, it added.

Water levels at several river basins were already above alert level, OCHA said.

Heavy rains and strong winds started to batter the area in the morning, according to the Mozambique National Meteorology Institute (INAM).

"There is already quite substantial flooding," Guy Taylor, a spokesman for the UN children's agency UNICEF, told AFP from Quelimane earlier on Saturday.

"We saw people with water in their houses, wading through knee-deep water. And that's just with this initial bit of rain."

On Friday, authorities said more than half a million people were at risk.

The storm was expected to drop up to 400 millimetres (16 inches) of rain over the next few days, more than twice the usual monthly rainfall.

According to the UN World Meteorological Organization (WMO), Freddy, which formed off northwestern Australia in the first week in February, was set to become the longest-lasting tropical cyclone on record.

It crossed the entire southern Indian Ocean and battered Madagascar from February 21, crossing the island before reaching Mozambique on February 24.

Following what meteorologists describe as a "rare" loop trajectory, Freddy then headed back towards Madagascar before moving once more towards Mozambique.

During the first deadly visit it destroyed, damaged or flooded more than 28,000 homes, affecting about 166,000 people.

In total, Freddy has so far killed at least 27 people -- 10 in Mozambique and 17 in Madagascar.

Taylor noted concern that renewed flooding could exacerbate a cholera outbreak that has killed at least 38 people and infected almost 8,000 since September.

The disease, which causes diarrhoea and vomiting, is contracted from a bacterium that is generally transmitted through contaminated food or water.