Aung San Suu Kyi's National League for Democracy party has retained support in its Yangon strongholds, but loyalty has weakened in ethnic minority areas, according to results of Sunday's by-election.

The country's election commission said the NLD took eight of 12 seats for the combined upper houses of the national parliament.

But it won only one of seven seats at stake in state assembles, where ethnic-focused parties performed strongly.

NLD's litmus test

The voting to fill a total of 19 seats was seen as a test of the democracy icon's popularity after a bumpy first year in office.

The military-backed Union Solidarity and Development Party, which led the previous government, won one lower house seat and one state assembly seat.

The Shan Nationalities League for Democracy won six seats, and the Arakan National Party and the All Nationalities Democracy Party got one apiece.

Still, one of the NLD's victories was to fill the seat won in 2015 by Suu Kyi, who had to give it up when she joined the Cabinet as state counsellor, the country's de facto leader.

The party stormed to power in a historic 2015 poll that ended half a century of brutal military rule.

Voters grow frustrated

But disillusionment with the administration has grown as the young government struggles to push through democratic reforms, kick-start the economy and ease unrest along the borders.

In a televised address earlier this week, Suu Kyi acknowledged the public's frustration with the slow pace of reforms and development. But she also reiterated her top priority of ending the ethnic conflicts that have kept Myanmar, also known as Burma, in a state of near-perpetual civil war.

Major rebel armies - engaged in clashes with the military in areas including Shan state - have refused to actively participate in her peace process.

Nobel Peace Prize winner Suu Kyi is also facing international criticism for her government's handling of a crisis in the Muslim-majority Rakhine region, where soldiers have blocked access for aid workers and are accused of raping and killing civilians.

mm/rc (AFP, AP)