(Recasts; adds U.S. market activity, quote, updates prices; changes byline, dateline, previous LONDON)
By Karl Plume
CHICAGO, Nov 2 (Reuters) - U.S. corn futures climbed to a one-week high on Thursday on improving export demand, although gains were limited by reports of higher-than-anticipated U.S. harvest yields.
Soybeans rose for a second day and notched a two-week high as expectations of lower U.S. yields and rising demand from China supported the market, while wheat rebounded from six straight lower sessions.
Chicago Board of Trade December corn were up 2-1/2 cents at $3.50-3/4 a bushel as 12:55 p.m. CDT (1755 GMT), supported by an uptick in export demand following the market's recent slump.
The U.S. Department of Agriculture on Thursday confirmed 1,356,360 tonnes in U.S. corn sales to Mexico for shipment in the current and next marketing years. That followed news of several corn purchases by South Korean importers.
"Corn is starting to get some value based buyers. Between Mexico and South Korea, we're getting more buyers showing up for grains, mainly for corn," said Rich Nelson, chief strategist with consultancy Allendale Inc.
However, plentiful supplies of the grain continue to hang over the market as several crop watchers increase their yield forecasts as the U.S. harvest has passed the halfway point.
Private analytics firm Informa Economics raised its 2017 corn yield estimate to 173.4 bushels per acre (bpa), from its previous monthly estimate of 170.5 bpa, three trade sources said. On Wednesday, commodity brokerage INTL FCStone raised its estimate to 173.7 bpa, from 169.2 previously.
The latest forecasts on U.S. soybean yields, however, have been flat to lower.
The USDA will update its official U.S. crop production estimates in a monthly report next week.
Actively traded CBOT January soybeans were 6-1/2 higher at $9.97-3/4 a bushel, briefly rising above the $10 mark for the first time in two weeks. The contract held above its 20-day moving average of around $9.90.
Soybean prices were also supported by the prospect of rising demand from China.
Chinese imports of oilseeds are forecast to grow to a record 99.8 million tonnes in 2017/18, up 1.3 million tonnes from the prior season, according to a report issued by the USDA's attache in China.
CBOT December wheat gained 8 cents, or 1.9 percent, to $4.26 a bushel, supported by short covering and technical buying after hitting a contract low earlier in the week.
(Additional reporting by Naveen Thukral in Singapore and Nigel Hunt in London; editing by David Evans and Chizu Nomiyama)