Nearly two-thirds of registered voters in Kabul apparently stayed away from the polls during Afghanistan's landmark legislative elections, an election official said on Thursday, as thousands of workers counted ballots under pressure from candidates' representatives.

Early reports from nearly all polling centers suggest nationwide turnout at about 53 percent - in line with earlier estimates - with some 6.6 million voters casting ballots in the first parliamentary elections in 36 years, United Nations Afghan chief electoral officer Peter Erben said.

However, the turnout in the capital, Kabul, appeared to have been only about 36 percent, Erben told a news conference.

The indications that nationwide turnout was sharply lower than 70 percent for last year's presidential election tempered celebrations of Sunday's vote as a key step to democracy, after decades of conflict and chaos.

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Observers, officials and human rights activists have said fears of violence, anger over the presence of powerful warlords on the ballot and distrust of politicians were among the factors that kept millions of Afghans away from the polls.

Erben reiterated his upbeat assessment, saying that in countries emerging from war, turnout in the first election is often higher than in the next vote.

But with turnout figures suggesting enthusiasm for the democratic process is not universal, UN and US officials have stressed the need to improve security and make swift progress in rebuilding the war-shattered country.

Workers began the painstaking process of counting the ballots on Tuesday and Erben said officials hope to have complete provisional results by October 4, despite logistical challenges.

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