WASHINGTON, Dec. 29 -- More than 975,000 Americans have enrolled in December in the Obama administration's healthcare online marketplace, pushing the total enrollment above 1.1 million, a senior government official announced on Sunday.

"More than 1.1 million people enrolled in a qualified health plan via the federally-facilitated marketplace from Oct. 1 to Dec. 24, with more than 975,000 of those enrolling this month alone," said Marilyn Tavenner, head of the Centers for Medicare and Medicaid Services, in a blog post.

"We experienced a welcome surge in enrollment as millions of Americans seek access to affordable health care coverage through new Health Insurance Marketplaces nationwide," said Tavenner, whose agency oversees the implementation of the Affordable Care Act, often dubbed as the "Obamacare."

After its debut on Oct. 1, the online marketplace, Healthcare. gov that aims at getting millions of uninsured Americans enrolled for health care coverage, has been plagued with technical problems and went almost out of service during the first two weeks.

"Our HealthCare.gov enrollment nearly doubled in the days before the Jan. 1 coverage deadline compared to the first few weeks of the month. December enrollment so far is over seven times that of October and November. In part, this was because we met our marks on improving HealthCare.gov," Tavenner added.

The website, the federal online marketplace serving consumers in 36 states, is key to Obama's signature healthcare overhaul aiming to get more uninsured Americans coverage. The remaining 14 states and the District of Columbia have built their own websites.