Boxer Amir Khan -- Heavily Armed Security In Pakistan ... To Take On Taliban

Boxer Amir Khan has landed in Pakistan -- where he's got a heavily armed security escort -- and plans to help rebuild the school that was terrorized by the Taliban.

Khan -- who has family in Pakistan -- was deeply affected by the massacre ... in which Taliban militants stormed a school and murdered 141 people ... including 132 children.

The 28-year-old already donated a pair of $45k gold boxing trunks to raise money for the school ... and scheduled an emergency trip to the country to help "fight the menace of terrorism."

The 2-time world champ touched down in Pakistan early Wednesday morning ... and immediately held a news conference -- telling reporters, "I want to show the world that we can improve Pakistan."

He added, "I'm here in this time to stand with the Pakistani nation. I've come here to prove that Pakistan is a safe country for sports. I also want to give the message that sports and education will take us forward."

Immediately following the conference, Khan went to a sports complex in Islamabad and met with local kids.