The loan -- up 66 per cent from the USD 1.8 billion agreed for 2015-2017 -- will help the Philippines build roads and other infrastructure, improve its basic education system and reform its capital markets, said the statement issued jointly with the Philippine government.
Bank president Takehiko Nakao said boosting lending to the country was in part aimed at "supporting the government in its effort to bring lasting peace and development" to the Catholic nation's Muslim south.
Parliament is currently debating a proposed law to grant minority Muslims self-rule in the violence-racked area, which President Aquino hopes will be passed before next year.
The government also plans to pour large amounts of aid to the region, and the ADB said it is now working with local authorities to prepare a development plan.
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The bank will also help the government raise adult literacy and improve job prospects for residents there, the statement added.
Rebuilding basic infrastructure, as well as improving literacy levels, would help the region attract business investment necessary to create jobs to help its people get out of poverty.