The Asian Infrastructure Investment Bank (AIIB) now has 109 members after its Board of Governors approved the applications of El Salvador, Solomon Islands and Tanzania on Tuesday.
The bank approved the applications of the three economies during its eighth annual meeting held in the Egyptian resort of Sharm El-Sheikh, the AIIB said in a statement.
"AIIB has a track record of successful collaborations with our members," said AIIB President and Chair of the Board of Directors Jin Liqun, adding that the addition of the three economies "will strengthen the AIIB community and support our collective mission to finance infrastructure for tomorrow."
The three countries will officially join the AIIB once they complete the required domestic processes and deposit the first capital installment with the bank, the statement said.
AIIB members now collectively account for 81 percent of the world's population and 65 percent of global gross domestic product, it reads.
The AIIB is a multilateral development bank whose mission is to finance the infrastructure that prioritizes sustainability. It began its operations in Beijing in January 2016.
The two-day annual meeting of the AIIB kicked off on Monday under the theme "Sustainable Growth in a Challenging World."