Myanmar says its army will “crush” an insurgent group that attacked four police stations in a western border region last week, the latest escalation in a tangle of slow-burning civil wars between the government and armed ethnic insurgencies.

The attacks Friday in the western state of Rakhine came less than three weeks after the government declared a temporary suspension of military operations against other armed groups in parts of the country’s north and east. Analysts see a familiar pattern, in which halting progress toward peace in one part of Myanmar is undercut by flaring violence in another.

The attacks on the police stations, carried out by an armed group called the Arakan Army, are part of a monthlong insurgency that has displaced thousands of civilians in Rakhine State. The campaign has “added another complicated level of complexity onto an already complicated situation, and revealed the depths of a Rakhine nationalism which has not been well understood since 2012,” said David Scott Mathieson, an independent political analyst in Myanmar.

Mr. Mathieson was referring to a year when violence flared between Rakhine Buddhists and Rohingya Muslims in Rakhine, leaving more than 100,000 people homeless. Both groups have long been marginalized by Myanmar’s Bamar ethnic majority, and the Arakan Army was formed about a decade ago by Rakhine nationalists who oppose Bamar-centric rule.