SINGAPORE (Reuters) - Singapore stocks edged up on Tuesday after two straight sessions of decline, led by a 5 per cent jump in shares of Noble Group, while losses in property plays weighed on sentiment.

The benchmark Straits Times Index edged up 0.2 per cent to 3,200.50 by midday, after touching a one-week low of 3,186.09 earlier in the day.

Noble rose as much as 5.3 percent to $1.285, snapping a two-day losing streak that followed a surge to the stock's 17-month high of $1.32 last week, after the company announced that China's largest grain trader COFCO Corp will buy a 51 per cent stake in Noble's agribusiness for an initial US$1.5 billion (S$1.9 billion).

Global Logistics Properties shares dropped 1.9 per cent, among the worst performing stocks on the index, while City Developments fell 1.2 per cent to a one-week low of $10.08 in its second day of decline.

OCBC downgraded CityDev to "sell" with a target price at $8.72, citing the deteriorating residential property market in Singapore.

"We anticipate increasing headwinds in the domestic residential space as both primary and rental markets continue to suffer from weakening supply-demand dynamics," OCBC analysts said in a research note. Singapore contributed to 60 per cent of the company's revenue in 2012, Thomson Reuters data showed.

They applauded CityDev's effort to diversify its business to overseas markets, but said it would take some time for the effort to bear any fruit.