San Francisco - Ten years after the horrific massacre at Columbine High School in Colorado, Americans remembered the tragedy Monday with memorial services, television segments and news reports pointing out that access to guns had become easier than ever.

Flags flew at half-mast across Colorado in remembrance of the 13 people killed and 23 others wounded when two disaffected students rampaged through the school killing students and teachers at will.

As the drama played out on national television, the attackers Eric Harris, 18, and Dylan Klebold, 17, killed themselves, leaving a shocked country to ponder the circumstances and policies that could have caused such a tragedy.

The memorial services kicked off Sunday night with a candlelight vigil at Littleton's Columbine Memorial and will conclude with a private service later Monday night next to the school for the families of the victims. Columbine High School was closed for the day, as it has been for every anniversary of the massacre.

"We cannot allow the lessons of this tragedy to fade with the passage of time," said Colorado Governor Bill Ritter.

However, gun control advocates maintain that the impetus the event provided to limit access to weapons was largely ignored, as former President George W Bush relaxed gun controls.

"It's easier for dangerous people to get dangerous weapons," said Daniel Vice, the senior attorney for the Brady Campaign, a national organization that lobbies for stricter gun controls.

Other groups that sprang up after Columbine also took the opportunity to get their message across.

Craig Scott, whose sister Rachel was killed in the massacre, recounted the horror of her death. Scott told CNN that the killers had mocked her for her faith. "They picked her up by her hair. 'Do you still believe in God?' they demanded. She said, 'Yes she does.' And then they shot her in the head," he told CNN.

In the aftermath of the killing, Scott's family started a group called Rachel's Challenge, that tries to teach students to reach out to those who feel isolated.

"The only reason I take use of media opportunities like this is that .. my family has a message to share since the shootings," he told CNN. "That you can reach out to someone feeling isolated by stepping out to reach that person." (dpa)