Weather forecasters said tropical storm "Milenyo" will bring heavy rains and wind gusts of up to 85 kph before making landfall tomorrow.
The islands of Samar, Dinagat, Leyte, Biliran and Siargao in the Visayas were also placed on storm alert.
Coastal waters will be rough and extremely dangerous, and residents were advised to seek higher ground because of big waves.
Those living in low-lying areas and near mountain slopes were alerted to the possibility of flash floods and landslides.
Milenyo will veer westward before making landfall over Aurora province tomorrow.
It will then cut across central Luzon and exit over the South China Sea.
In Bicol, some 343 passengers in the ports of Masbate, Matnog and Tabaco were stranded after Milenyo intensified and threatened Samar and other nearby Visayan islands.
Capt. Rodolfo Isorina, Coast Guard commander for Bicol, said 253 passengers were stranded in Masbate port, including 15 trucks, two small cars and five vessels, while another 44 passengers were stuck at Matnog port in Sorsogon, including eight trucks, seven small cars one passenger bus and one vessel.
Another 45 passengers were stranded as well as one truck, two small cars and five vessels at the Tabaco Port in Albay, he added.
Isorina said that the different Coast Guard commanders were closely monitoring the situation and have not allowed vessels to leave port.
As of 11 a.m. yesterday, Milenyo was 220 kilometers east of Borongan in Eastern Samar, with maximum sustained center winds of 85 kilometers per hour and gustiness of up to 100 kph. The tropical storm is moving northwest at seven kph.
Placed under storm signal No. 1 are Catanduanes, Sorsogon, Albay, Masbate, and Ticao Island, the Leyte provinces, and the islands of Biliran, Camotes, Dinagat and Siargao.
The Samar provinces were placed under tropical storm signal No. 2. — Celso Amo, Helen Flores, AP