Polls have opened in Burmese by-elections that promise to be the most open contest in decades, with Aung San Suu Kyi among those standing. Her National League for Democracy (NLD) is contesting all 45 seats, vacated when politicians joined the military-backed civilian government. It is the first time Ms Suu Kyi has run as a candidate for political office. It is also the first time international observers have been allowed to monitor elections in modern Burma. The European Union looks set to ease some sanctions on the country if Sunday's elections go smoothly. Ms Aung San Suu Kyi spent a total of 15 years under house arrest after the military refused to accept the NLD's landslide general election victory in 1990. While only a fraction of seats are up for grabs, the NLD is expected to enter parliament as the official opposition. With tens of thousands of people turning out to back Ms Suu Kyi and her fellow NLD candidates, the by-elections have taken on a huge significance, says the BBC's Rachel Harvey in Rangoon. 'Not irreversible' On Saturday, election officials around the country were making final checks at polling stations, ensuring ballot boxes and booths were ready. "We're preparing the election on 1 April to be free and fair," election official Maung Maung Than told the Associated Press news agency. "We'll make it free and fair, I believe this." Ms Suu Kyi is standing for a lower house seat in the Kawhmu Township constituency outside Rangoon. She arrived there on Saturday in a convoy of NLD cars, plastered with party stickers. Small groups of people gathered to welcome her, wearing NLD T-shirts and waving party banners and portraits. The NLD boycotted the 2010 general election on the grounds that election laws were unfair. Earlier, Ms Suu Kyi described this year's election campaign as not ''genuinely free and fair" but said she and the NLD did not regret taking part. "Still we are determined to go forward because this is what our people want," she said. At the same time, she warned that Burma's democratisation was "not irreversible". 'Exciting prospect' A small number of representatives from the Association of South-East Asian Nations (Asean), along with the EU and US, have been invited to observe polling. More than 100 foreign journalists are believed to have received permission to cover the vote. EU Trade Commissioner Karel De Gucht said political sanctions on Burma were mostly "aimed towards individuals" and could be eased when EU foreign ministers met in Brussels on 23 April. The lifting of such sanctions could "even happen with immediate effect", he told AFP news agency. "The European Union and also myself, I am excited by the prospect that finally, hopefully Myanmar [Burma] citizens will get more freedom," Mr De Gucht added. "Political freedoms and economic freedoms always go together."