KANDAHAR, Afghanistan — The Afghan military has suffered its worst loss of the year in southern Afghanistan, with at least 40 security force members killed in a Taliban attack this past week, but senior officials had still not released a death toll two days later, according to residents and functionaries from the area who spoke on Sunday.

The national authorities and those at the provincial level in Helmand confirmed that an attack occurred in Sangin District, one of the most heavily contested areas in the country, on Friday night, but they either refused to give any details or claimed not to have any as of Sunday.

It was yet another indication that the Taliban were continuing to attack Afghan government forces aggressively even as they have entered peace negotiations on an American withdrawal from the country, with another round of talks expected in Qatar this month.

Some estimates put the number of security forces killed in Sangin late Friday and early Saturday at 65, including 48 Afghan National Army soldiers, 10 pro-government militia fighters and seven police officers, with 43 others wounded, according to Mohammed Hashim Alokozai, an Afghan senator and member of the Defense Committee in Parliament, who is from Sangin.