The spot market opened at 6.4405 per dollar and changed hands at 6.4366 per dollar by the 0830 GMT domestic close, the strongest since Dec. 9, 2015.

The Chinese currency has risen about 1.1 percent against the dollar this year, after a roughly 6.8 percent gain during 2017, reversing three straight years of depreciation.

The People's Bank of China (PBOC) recalibrated the template for daily yuan fixings last week to nullify a discretionary counter-cyclical factor it introduced into the formula last year to contain the currency's decline.

That, analysts said, meant the yuan would move in line with the currencies of its trading partners and was seen as an attempt by authorities to cap the currency.