KABUL, Afghanistan (April 10, 2012)--Spring temperatures are producing an uptick in attacks across Afghanistan, including two on Tuesday that killed at least 15 people in the south and west.

Four policemen were killed at a local police office in Helmand province in the south.

Another three policemen and eight civilians died in a large blast in Herat province in western Afghanistan.

The Taliban claimed responsibility for both attacks in telephone messages to the media.

Militants have been targeting Afghan and NATO security forces as they fight to assert their power and undermine U.S. efforts to try to build up Afghan forces.

Afghanistan's police and army are increasingly shouldering the job of providing security with the planned exit of most foreign combat troops by the end of 2014.