Millions of people are at risk from a strong typhoon set to smash into the northern Philippines this weekend which could bring floods, landslides and huge waves to the disaster-prone nation, rescue workers said Wednesday.

Emergency workers have been deployed in the northern tip of Luzon, where Typhoon Ompong (international name Mangkhut) is expected to make landfall on Saturday.

It is currently barreling across the Pacific with winds of 205 kilometers per hour (kph), and gusts reaching 255 kph.

"We're worried for the 10 million people in the Philippines living in the path of this destructive storm," said Richard Gordon, chairman of the Philippine Red Cross.

The state weather service said Mangkhut will be the strongest typhoon this year, peaking at gusts of up to 270 kilometers an hour on Thursday before easing to still-dangerous velocities as it approaches land.

The Philippine Red Cross estimates three million Filipinos live in the direct path of Mangkhut, communications officer Mary Joy Evalarosa told AFP.

She said seven million others are at risk in the country, with the typhoon expected to boost the intensity of seasonal monsoon rains that have already caused widespread flooding in central Luzon, a mainly farming region north of capital Manila.

An average of 20 typhoons and storms lash the Philippines each year, killing hundreds of people and leaving millions in near-perpetual poverty.

Tropical Storm Yagi and monsoon rains last month caused heavy flooding across central Luzon as well as parts of Manila, where an overflowing river swept away cars in one district.

The country's deadliest on record is Super Typhoon Yolanda (Haiyan), which left more than 7,350 people dead or missing across the central Philippines in November 2013.

The state weather service said heavy rains and strong winds are expected from Friday over the north and centre of Luzon, along with rough seas on the coasts.

The International Federation of Red Cross and Red Crescent Societies said it expects "substantial damage" on the Philippine path of Mangkhut.

Storm surges of up to seven meters (23 feet) are expected to hit coastal areas, it said, while heavy rains could trigger landslides and flash floods.

The civil defense office in Manila said towns and cities on Mangkhut's path are preparing government buildings as evacuation centers, stockpiling food and other emergency rations, and preparing rescue teams and equipment.

Mangkhut is predicted to reach China's southern coast around Sunday, according to the Hong Kong Observatory.