KABUL: President Hamid Karzai widened his lead over his main challenger in election returns released Saturday, creeping toward the 50 percent mark that would enable him to avoid a run-off in the divisive presidential contest.

Karzai’s top challenger Abdullah Abdullah stepped up his fraud charges, raising doubts whether the former foreign minister’s followers would accept the incumbent if he wins in the first round.

Accusations of fraud in the Aug. 20 vote have poured into the Electoral Complaint Commission, which must investigate the allegations before final results can be announced.

Fraud allegations from Abdullah and other presidential candidates as well as low turnout in the violent south could strip the election of legitimacy, not only among Afghans but also among the United States and its international partners that have staked their Afghan policies on support for a credible government.

A widely accepted Afghan government is one of the pillars of President Barack Obama’s strategy to turn the tide of the Taleban insurgency. The election controversy has boiled over at a time of rising US and NATO casualties, undermining support for the war in the US, Britain and other countries with troops here.

British Prime Minister Gordon Brown paid a surprise visit Saturday to British troops in southern Afghanistan’s Helmand province, hoping to counter critics who accuse his government of failing to support Britain’s mission here. A British Marine was killed by a bomb in Helmand on the day of the prime minister’s visit, the Ministry of Defense said in London.

Figures released Saturday show Karzai with 46.2 percent of the votes against Abdullah’s 31.4 percent. The results are based on 35 percent of the country’s polling stations, meaning the percentages could still change dramatically.

Meanwhile, Afghan ex-militia chief Abdul Rashid Dostum, who returned to the country last week to campaign for Karzai, has again left, his spokesman Naqibullah Fayeq said on Saturday.

The United States and United Nations had both expressed concern when Dostum, a leader of the ethnic Uzbek community and former Communist general who led militias through decades of civil war, flew into the country on the eve of the vote.

Dostum had been living in Turkey for months, until the Afghan government announced hours before his return that he was free to come home. It had never been made clear whether his exile was self-imposed or ordered.

He has denied numerous accusations of human rights abuses, including that his forces were responsible for killing Taleban prisoners in 2001. The United States said when he returned that it was concerned about his rights record and the prospect of him possibly being given a post in Karzai’s government.

Fayeq said one of Dostum’s goals in Turkey would be to meet US officials and clear his name over the rights accusations.