Mourners and world leaders gather in South Africa ahead of Mandela memorial at stadium

Mourners are gathering at a stadium near Johannesburg for a massive memorial service honoring Nelson Mandela.

A light rain fell Tuesday as mourners gathered at FNB Stadium in Soweto, the Johannesburg township that was a stronghold of support for the anti-apartheid struggle that Mandela embodied.

Singing, joyous crowds are swelling in the stands despite the rain. Workers still were welding at a VIP area as the first spectators arrived.

Some 100 world leaders are expected. U.S. President Barack Obama landed in South Africa hours before the event was due to start.

Police have promised tight security, and are patrolling a wide perimeter around the stadium. Even so, the first crowds entered the stadium without being searched.

Mandela died Dec. 5 at age 95. He will be buried Sunday.