(Reuters) - Technical glitches and heavy internet traffic slowed Tuesday's launch of new online insurance exchanges at the heart of President Barack Obama's healthcare reform, showcasing the challenge of covering millions of uninsured Americans.

The opening itself represented a victory for Obama's signature domestic policy achievement after years of attack from Republican foes and delays in building the technology infrastructure to support sites in 50 U.S. states. It defied a partial federal government shutdown precipitated by Republican efforts to delay the law's implementation.

[...]

Reuters checks in at least 47 states throughout the day turned up frequent error messages or traffic overload notices, particularly for 36 sites run by the federal government. One frequently observed glitch involved a page asking the user to answer security questions that either went blank or would not accept new data. Kansas officials urged residents to wait a few weeks for the "bugs" to be worked out before enrolling.

The Department of Health and Human Services said 2.8 million people visited the federal HealthCare.gov since midnight, with 81,000 reaching out to call centers and 60,000 requesting live chats. The department did not provide details on the source of the traffic or the number of visitors who applied for health insurance, but said it was working to speed up the site.

"We think we're off to a good start," said Marilyn Tavenner, head of the Centers for Medicare and Medicaid Services, which oversees the new exchange.

The performance of state-run exchanges was mixed, with users in Connecticut, Rhode Island and California able to create profiles. Kentucky said it had processed more than 1,000 insurance applications, while Colorado said 1,300 user accounts had been created. Maryland delayed its launch by hours. When it went live, access stalled for some users.

Chris Carlin, a 25-year-old student and part-time worker from the Los Angeles area, said he was unable to access health plan details on the California exchange, but would keep trying.

"This is a huge deal for me," he said. "I haven't had health insurance since high school - that's been 7 years."

Anna and Dennis Franks, a Utah couple in their 60s, drove about 40 miles from their home in Ogden with friends to attend a marketplace launch event in Salt Lake City. The couple was unable to compare health plans or enroll online, but they were undeterred. "We'll wait for all the hoopla to settle down," Dennis Franks said.

Jonna Bady and Antonio Hill, a couple in their 20s, made an appointment to enroll on Tuesday in Chicago, and expected to qualify for Medicaid. The website was down when they arrived.

Asked why she came on the first day of open enrollment, Bady said: "It's important. I know other people are going to come. I want to get in early."