MANILA (BLOOMBERG) - A super typhoon in the Pacific is gaining even more strength and is forecast to barrel through the northern Philippines later this week before heading towards Hong Kong and southern China.

Mangkhut, classified by the Hong Kong Observatory as a maximum category 5 super typhoon, is now forecast to pack maximum winds of 250 kilometres per hour by Friday (Sept 14) before gradually weakening.

That compares with Tuesday's reading of 230kph.

The typhoon, expected to be closer to south China by the weekend, will bring heavy rains and storm surges on its trail. It can affect as many as 43.4 million people, according to the United Nations' Global Disaster Alert and Coordination System.

The Philippines is anticipating that Mangkhut will be as strong as Typhoon Haiyan, prompting the preparation of food, supplies and rescue efforts as well as 1.7 billion pesos (S$43.4 million) in stand-by funds, according to the disaster agency.

In 2013, Super Typhoon Haiyan killed more than 6,300 people in the Philippines.

Mangkhut is forecast to be the strongest typhoon to hit the Philippines this year and is threatening farmlands in Northern Luzon just before the rice and corn harvest. The staple grains are the second-biggest item in the Philippine consumer basket, and record prices boosted inflation to 6.4 per cent in August, the fastest pace since 2009.

The storm could cause as much as 13.5 billion pesos in damage to crops, Agriculture Secretary Emmanuel Pinol wrote on his Facebook account on Tuesday.

Mangkhut, to be named Ompong once it enters the Philippines' area, is now forecast by the US military's Joint Typhoon Warning Center to bring top winds of 150 knots (277kph) with maximum gusts of 180 knots.