Mount Mayon, a volcano in Albay province in the coconut-growing central Bicol region, has been erupting since Saturday and the number of people fleeing their homes had more than doubled on Tuesday to about 25,000, said Albay Governor Al Francis Bichara.
The National Disaster Risk Reduction and Management Council gave a smaller estimate, saying there were close to 22,000 evacuees.
Placing the province under a state of calamity will give the province access to extra funds.
"This kind of eruption, it will take about weeks, so we have to sustain the operations in the evacuation centres," Bichara told ANC news channel. "We need to use the calamity funds."
The provincial government has also expanded its suspension of school classes to more towns around the 2,462-metre (8,077-foot) volcano, about 340 km (210 miles) southeast of Manila.
Class suspensions have allowed the government to use schools as temporary shelters.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)
Get the latest election news, live updates and election schedule for Lok Sabha Elections 2019 on ndtv.com/elections. Like us on Facebook or follow us on Twitter and Instagram for updates from each of the 543 parliamentary seats for the 2019 Indian general elections. Election results will be out on May 23.