Officials have warned of possible outbreaks of cholera and diarrhoea.
Bulten said the government had put early warning and contingency measures in place ahead of the wet season, and aid agencies had enough humanitarian stocks - including food, blankets and water purifying tablets - in the country for about two weeks.
Radio Mozambique reported 10 of 17 towns in the Machanga district, 100km south of the port city of Beira, had been flooded by waters from the Save River.
The radio said the Mopeia district, 225km north of Beira on the lower Zambezi River, had been completely submerged and emergency services had intensified rescue operations in the area. The government declared a major alert on January 3.
Last week, the UN Children's Fund (Unicef) last week appealed for $2.4m to help flood victims.
Mozambique's National Institute of Disaster Management has estimated a further 60,000 people could be at risk from floodwaters.
The flooding has also affected neighbouring Zimbabwe and Zambia, leaving about 3,000 people homeless in Zambia, while three were killed in Zimbabwe.