Thousands of people have marched through the southern Colombian city of Tumaco in protest at a series of deadly attacks.<br /> <br />Tumaco is one of a number of areas being targeted by bombs and mortars. <br /> <br />At least 18 people have been killed. <br /> <br />The government says Farc guerrillas are to blame.<br /> <br />Al Jazeera's Tom Ackerman reports.
