Onshore yuan weakened 222 basis points to 6.7379 against the U.S. dollar Monday, the biggest drop in a week and hitting the lowest level in six years. 

Meanwhile, off-shore yuan fell to 6.7438 against the greenback. Analysts say the main driver is the strong U.S. dollar, which inched up to a seven-month high against a basket of currencies on Monday, retaining momentum from upbeat U.S. data last week.

They added that as expectations rise of a December rate hike by the Fed, the Chinese yuan is going to remain weak against the U.S. dollar in the short term.