Myanmar has promised to "seriously consider" allowing Southeast Asian observers for by-elections marking the opposition's return to mainstream politics, the ASEAN regional bloc said Tuesday.

The April 1 polls, which will see Aung San Suu Kyi stand for a seat in parliament for the first time, are viewed as a key test of the government's commitment to budding reforms.

The Association of Southeast Asian Nations (ASEAN) said in a statement that Myanmar President Thein Sein made the pledge to its visiting Secretary-General Surin Pitsuwan during talks in the capital, Nay Pyi Daw.

"We will seriously consider having observers from ASEAN during the April elections," Thein Sein said.

A 2010 election, which swept the army's political allies to power, was marred by widespread complaints of cheating and intimidation.

Foreign election observers and international media were not allowed into the country for that vote, which was denounced by Suu Kyi's opposition party and Western powers as lacking legitimacy.

Suu Kyi's National League for Democracy (NLD) party held a news conference on Monday to warn that the fairness of the April vote was also under threat because it was being denied the use of suitable venues for campaign rallies.

But, hours later, the NLD said authorities had eased the restrictions in a turnaround it described as "very significant."

The opposition cannot threaten the ruling party's majority, even if it takes all 48 available seats in the by-elections, but a Suu Kyi win would lend legitimacy to the fledgling parliament.

Suu Kyi's decision to stand for a seat in parliament is the latest sign of dramatic change taking place in the country.

The regime has surprised observers with reforms, including signing cease-fire deals with ethnic minority rebels and releasing hundreds of political prisoners.

The upcoming polls are being held to fill places vacated by those who have since become government and deputy ministers.