President Hamid Karzai widened his lead over his top challenger Wednesday after Afghan officials released more partial vote results. The president's new total pushed him closer to the 50 percent threshold that would allow him to avoid a two-man runoff. The Independent Election Commission released its second batch of results from last week's presidential election. More will be released in coming days, and final certified results won't be ready until at least mid-September, after the dozens of serious complaints of fraud have been investigated. Low voter turnout and the fraud allegations have cast a pall over the election. Top challenger Abdullah Abdullah has accused Karzai of widespread rigging, including ballot stuffing and voter intimidation, claims Karzai's camp has denied. The latest returns boost Karzai's standing to 44.8 percent. Abdullah now has 35.1 percent. The count is based on returns from 17 percent of polling stations nationwide, meaning the results could still change dramatically. Before the election commission released results Wednesday, Ramazan Bashardost - a candidate likely to come in third - stood up at the news conference and told officials they were breaking the law by announcing results before the Electoral Complaints Commission carries out its work. Millions of Afghans went to the polls last Thursday to vote in the country's second-ever direct presidential election. Militants launched dozens of attacks across the country, shutting down some polling sites and appearing to dampen turnout. This summer has been Afghanistan's most violent since the 2001 US invasion. President Barack Obama ordered an additional 21,000 troops to the country this year, in part to help secure the elections. But violence has continued to rise. The Taliban on Wednesday denied any responsibility for a major bombing that killed at least 43 people and wounded 65 in southern Afghanistan's largest city just after dark Tuesday. The explosion ripped through a central area of Kandahar two hours after the first batch of election results were released. Rescue workers were still pulling out injured people early Wednesday. The blast occurred in a district that includes UN facilities and an Afghan intelligence office. Kandahar is the spiritual home of the Taliban, but the group said it had no involvement in the attack. The Taliban often denies it was behind attacks that kill civilians. "We are denying responsibility, and condemn this attack in which innocent civilians were killed," Taliban spokesman Qari Yousef Ahmadi wrote in a text message sent to an Associated Press reporter. Kandahar Gov. Tooryalai Wesa said officials couldn't yet say who was responsible. The attackers "have no conscience or families," he said. "The area was full of innocent civilians. There were no important government institutions," said Wesa. Karzai sent the country's interior minister to Kandahar to give government payments to victims. The Interior Ministry said the blast was from remote-controlled explosives planted in a truck. Local officials had said a cluster of five vehicle bombs caused the blast. An Afghan employee of the International Committee of the Red Cross was killed in the explosion, the group said. "Last night's blast is yet another indication of the suffering that civilians all over Afghanistan have to endure," the Red Cross said in a statement. The latest presidential returns are based on partial results from 28 provinces, but few votes have been counted from Kandahar and no votes from Helmand, two areas that would boost Karzai's totals. The complaints commission is investigating allegations of vote rigging. The commission has received more than 1,400 complaints, more than 150 of which could affect the vote's outcome, said spokeswoman Nellika Little. Some observers worry Abdullah supporters could vent fury if he comes in second with no chance at a runoff. The latest results hew closely to an opinion poll taken in July that showed 44 percent of Afghans would vote for Karzai, and 26 percent for Abdullah. The poll of 2,400 people was funded by the International Republican Institute, a non-governmental organization that receives funding from USAID, the US government aid arm. The poll had a margin of error of plus or minus 2 percentage points.