KIEV, Dec. 1 - Royal Dutch/Shell Plc will invest $100 mln to search for natural gas in Ukraine in a joint project with Naftogaz Ukrayiny, the state oil and gas company, according to an agreement signed Thursday.

The agreement would allow Shell and Naftogaz to jointly explore for gas in the central and eastern parts of Ukraine on a total area of 31,000 sq. km, Naftogaz reported.