Feb 19 (Reuters) - Airports in China's biggest cities logged the fastest monthly passenger growth in January in at least two years as more travellers took to the skies before, and during, the week-long Lunar New Year holidays.

Analysts warned however that rapid expansion of airports throughout the country, and the threat of a bird flu outbreak, could reduce passenger traffic for the rest of the year.

Shanghai International Airport Co Ltd 600009.SS , which operates the airport in China's financial hub, said on Wednesday passenger numbers rose 17.5 percent in January from a year earlier to 4.15 million, the faster pace of growth since January 2011.

The number of passengers boarding international flights at the airport in January also increased 20.7 percent year-on-year, the company said in an exchange filing.

The Lunar New Year holiday spanned Jan. 31 to Feb. 6, while last year it fell between Feb 9 and 15.

Other Chinese airports also saw similarly strong passenger traffic.

Beijing Capital International Airport Co Ltd 0694.HK , China's biggest airport which sees more than six million travellers a month, said passenger numbers grew 9.2 percent in January from the same month a year ago, the fastest pace since April 2011, company data showed.

Shenzhen Airport Co Ltd 000089.SZ in the southern boomtown saw the strongest growth in passenger numbers in more than four years. Passenger numbers rose 18.1 percent to 2.93 million in January, its busiest month since November 2009.

Other airports in southern China, home to some of the country's most popular tourist destinations, also saw higher passenger traffic.

Guangzhou Baiyun International Airport Co Ltd 600004.SS reported January passenger numbers increased 14 percent from a year earlier, the fastest pace of growth in about two years.

Hainan Meilan International Airport Co Ltd 0357.HK in the southern tropical island recorded a 33.3 percent jump in passenger traffic, the fastest growth in more than two years.

(Reporting by Meg Shen in HONG KONG and Lee Chyen Yee in SINGAPORE; Editing by Miral Fahmy)

((meg.shen@thomsonreuters.com)(852-28436901)(Reuters Messaging: meg.shen.thomsonreuters.com@reuters.net))

Keywords: CHINA AIRPORTS/