LONDON—Royal Dutch Shell PLC is facing two lawsuits over its activities in Nigeria, after lawyers acting for a Niger Delta community whose land and water was polluted from a 2009 oil spill lodged a series of actions against the Anglo-Dutch giant in Port Harcourt and a separate suit was filed in London over two earlier spills in the same region.

The claims are the latest attempt by residents from the oil-rich Delta to seek restitution from foreign oil companies. Shell's operations there have long been criticized by environmental...