Cross-border incidents in the fighting have strained ties between the neighbours.
They have also proved problematic for President Thein Sein, who has ambitions to sign a nationwide ceasefire with many of the country’s armed ethnic groups before a general election on Nov 8.
On Tuesday, a majority of parliament members backed the motion to continue martial law in the Kokang region of Shan state. Martial law gives the military sweeping judicial and administrative powers.
The measure was needed because of continued instability in the region, said Shwe Mann, the embattled speaker of parliament.
President Thein Sein declared a three-month state of emergency and imposed martial law in the region on Feb 17 after fighting broke out between the Myanmar military and the Myanmar National Democratic Alliance Army (MNDAA).
Parliament voted to extend martial law for the first time in May. The MNDAA declared a unilateral ceasefire the following month after coming under pressure from Beijing to end the conflict, but clashes have since been reported.