Suspected Taliban militants on Friday shot dead a candidate in Afghanistan's national elections, and the Islamic guerrilla group warned people to boycott Sunday's voting or risk being hurt in attacks on U.S.-led forces.

The candidate, Abdul Hadi, who was running for a seat in the National Assembly, was killed early in the morning in the southern province of Helmand, provincial spokesman Mohammad Wali Alizai said. He was the seventh candidate around the country to be killed.

"The gunmen called at his house, and when he came out, they opened fire and killed him," Alizai said, adding that the attackers were believed to be Taliban guerrillas.

Militant violence has been the main worry leading to the landmark parliamentary and provincial elections. More than 1,000 people -- mostly militants, but also including about 50 U.S. troops -- have been killed this year, the bloodiest period since the Taliban was ousted from power in 2001.

The Taliban, which has denounced the elections, asserted responsibility for Hadi's death.

"He supported the Americans and he was a candidate for the Wolesi Jirga," or lower house of parliament, Taliban spokesman Abdul Latif Hakimi said by telephone from an undisclosed location.

The Taliban has asserted responsibility for the assassinations of several other candidates. The group said it will not target polling stations, but Hakimi said Afghans risked being hurt in attacks on foreign "occupation" forces and urged them to boycott the elections.

Security has been stepped up, with about 100,000 troops set to guard as many as 12.5 million voters. About 5,800 candidates are running in the elections, the final step in a three-year political process overseen by the United Nations.

Meriam Murad, an Afghan singer, performs at a concert in Kabul organized by the Joint Electoral Management Body, the group charged with overseeing Sunday's elections.