The Philippines and Taiwan are braced for Typhoon Usagi, which meteorologists say could become the most powerful typhoon of 2013.

The typhoon was 560km (350 miles) east-southeast of Taiwan and 360km (225 miles) from the northern Philippines on Friday morning, weather officials said.

Both Taiwan and the Philippines have issued alerts and warned boats to exercise caution. The tropical hurricane is expected to hit China over the weekend.

Typhoon Usagi has wind speeds of up to 175 km/h (109 mph)

Typhoon Usagi had wind speeds of up to 175 km/h (110 mph) and gained strength early on Friday, Pagasa, the Philippine government's weather agency, said.  Philippine officials have issued storm warnings for flash flooding, landslides and storm surges for several northern provinces.

Emergency and health personnel in some provinces have also been placed on standby, the National Disaster Risk Reduction and Management Council said.

Meanwhile, Taiwan's Central Weather Bureau issued a land warning on Friday morning, and forecast heavy rainfall for northern and eastern Taiwan.

China's State Oceanic Administration has issued a class I emergency response for the typhoon, its highest maritime disaster response level, state media report.

China's National Meteorological Centre has also issued a yellow alert in its weather warning system.

In August, at least two people died and thousands lost their homes after Typhoon Utor hit the northern Philippines.

Typhoons are common during the summer in parts of East Asia, where the warm moist air and low pressure conditions enable tropical cyclones to form.

(Source: BBC)