The military said fighting flared up earlier this month after one of its officers was killed in an ambush by the KIA, prompting it to deploy troops to clear areas along supply lines.
President Thein Sein's reformist government has struck a series of tentative peace deals with major rebel groups in the country, which has been wracked by civil conflict since independence from Britain in 1948.
After numerous rounds of talks, the government and Kachin rebels signed a seven-point plan in May 2013 aimed at ending hostilities.