LONDON (Reuters) - British Prime Minister Boris Johnson told German Chancellor Olaf Scholz that Western "inaction or underreaction" in response to Russia invading Ukraine would have unthinkable consequences, a spokeswoman for his office said on Thursday.

       Johnson held calls with Norway's Prime Minister Jonas Gahr Stoere and Germany's Scholz to discuss sanctions after Russian forces invaded Ukraine in a massed assault by land, sea and air.

       "Prime Minister (Johnson) underscored that western inaction or underreaction would have unthinkable consequences. The leaders agreed to stay in close contact and to discuss our response further in this afternoon's meeting of G7 leaders," a Downing Street spokeswoman said in a statement.

       (Reporting by Kylie MacLellan; writing by Muvija M)