The Association of South East Asian Nations will send 23 election observers to Myanmar this month at the government's request, ASEAN said.

Forty-eight Parliamentary seats have been left vacant because the elected members were appointed to fill Cabinet posts and other executive positions in the central government.

"Myanmar has urged relevant countries to lift their sanctions and allow the country to pursue its development and to improve the living standards of its people," ASEAN said.

The agreement was first discussed during a meeting in February between ASEAN Secretary-General Surin Pitsuwan and Myanmar President Thein Sein during Surin's visit to Myanmar.

The ASEAN statement says the two leaders agreed that such a move "would boost transparency, which will add to the international goodwill that Myanmar has attracted so far."

The polls promise to be a test for how far Myanmar's nominally civilian government of former junta leaders are willing to go to hold an election recognized internationally as free and fair.

ASEAN's statement acknowledged that "the April by-election has attracted a lot of attention."

During his visit to Myanmar, Surin met the 1991 Nobel Peace Prize laureate Aung San Suu Kyi who, as leader of opposition party National League for Democracy, is contesting a seat in the election April 1.

Suu Kyi and her NLD party won a national election in 1990 but were refused power by the ruling military government.

She wasn't allowed to run in the November 2010 national election because she was under house arrest. But the government since has allowed her greater freedom than before to comment on the political situation.

Although many Western countries called the November 2010 national election process and result fraudulent, the government has been making efforts to show it is moving toward a more open society and political structure.

Suu Kyi, 66, has welcomed the move by Sein toward more open democracy but cautioned a lot more must be done. In particular, she wants an end to the 25 percent of parliamentary seats reserved for military members appointed by the government, itself made up former junta leaders who resigned their commissions to run as civilians.

Tomas Ojea Quintana, the U.N. special envoy on human rights in Myanmar, recently told the U.N. Human Rights Council in Geneva that the elections would be a "key test" for the government which took office in January 2011.

"It is essential that they are truly free, fair, inclusive and transparent," he said.

"It is clear that there are ongoing and serious human rights concerns that remain to be addressed," said Quintana. "These cannot be ignored in the rush to reform and to move forward."

Press freedom remains a concern with the government planning to sue The Voice magazine over allegations of corruption in the Ministry of Mines, a report by the Irrawaddy news Web site, published from Thailand, said.

The state-run The New Light of Myanmar newspaper said the Ministry of Mining denied corruption allegations.

"Amid the country moving forward to full peace and development with discipline of democracy, it tarnishes the dignity of the ministry and is not ethical for the media to write like this," a statement from the Ministry of Mines said.