(Adds Hasina votes, arrests, details)

By Anis Ahmed

DHAKA, Dec 29 (Reuters) - Tens of millions of Bangladeshis streamed to the polls on Monday for an election that returns the country to democracy after two years of emergency rule and tests whether it has moved beyond a history of political violence.

An alliance led by former prime minister Sheikh Hasina of the Awami League has the edge in the vote for seats in parliament, most observers say. Others predict neither she nor rival and fellow ex-PM Begum Khaleda Zia will have an immediate majority.

Hasina cast her vote at a Dhaka college half an hour after polling started at 8 a.m. (0200 GMT). Khaleda was expected to vote soon at a different station.

Voting was peaceful and turnout was heavy in an almost festive atmosphere, Reuters reporters at various polling points said. Hundreds of voters waited in line at some stations.

At polling points in the capital Dhaka, people had begun queuing for more than an hour before voting started.

The impoverished South Asian nation of more than 140 million people has a history of questionable elections, sporadic periods of military rule and politically motivated violence.

Post-vote turbulence, whether tied to jockeying for position in a hung parliament or to street violence, could get in the way of a new government tackling such challenges as reducing corruption and improving the economy in a nation where some 45 percent of the people live below the poverty line.

The outgoing army-backed interim government -- which took over amidst political violence in January 2007 and cancelled an election due that month -- says that when it comes to voting procedure and safety, this time things will be different.

About 200,000 local and 2,000 foreign monitors are at the polling centres to check procedures.

The latter include first-time-ever anti-cheating measures like picture ID cards for the 81 million eligible voters.

Officials in northern Bangladesh said they had detained several people on Sunday night for trying to "buy votes" for various candidates.

In one such incident, police arrested a man whose brother is contesting the polls, at Kurigram, about 400 km (240 miles) north of Dhaka.

"We caught him giving out money to poor villagers to support his brother," one official told Reuters.

BLANKET SECURITY

In eastern Brahmanbaria district, a rural council chairman, Mohammad Jahangir, told Reuters by telephone: "There is no lack of enthusiasm. Security has been tight with police guarding the polling centres since Sunday night."

Bangladesh has deployed 50,000 troops, 75,000 police and 6,000 members of its elite Rapid Action Battalion along with other auxiliary forces for security.

"In some sensitive areas we have also kept bomb disposal squads on standby," a senior police officer said on Monday, declining to specify the locations.

Some analysts are concerned that even if the election itself goes smoothly, disgruntled backers of the losers will take to the streets, as has happened in the past.

Hasina and Khaleda alternated in power for 15 years through to 2006. Critics say they barely dented Bangladesh's problems, in a large measure because their parties took to the streets in protest and strikes when out of office.

Analysts say the women's policy differences are actually small and to attract much needed investment and aid what matters now is less who wins than post-election stability and peace.

Polls close at 4 p.m. (1000 GMT). Counting begins on Monday evening but results are not expected until Tuesday. (For related stories click on [ID:nSP347930]) (Additional reporting by Nizam Ahmed, Serajul Islam Quadir and Ruma Paul in DHAKA and Hasibur Rahman Bilu in BOGRA; Writing by Jerry Norton, Editing by Dean Yates)

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