PORT-AU-PRINCE, Haiti (AP) -- United States first lady Michelle Obama made a surprise visit yesterday to the ruins of the Haitian capital, a high-profile reminder that hundreds of thousands of people remain in desperate straits three months after the devastating earthquake.

The first lady and Jill Biden, wife of Vice President Joe Biden, took a helicopter tour of Port-au-Prince, where hundreds of thousands of people are still homeless because of the quake, before landing at the destroyed national palace to meet President Rene Preval. They later met with students whose lives have been upended by the disaster and walked along a vast, squalid encampment of families living under bed sheets and tents.

"It's powerful," Obama told reporters. "The devastation is definitely powerful."

Obama and Biden's visit is intended to underscore US commitment to the Haitian reconstruction effort and to thank American officials who have worked in the country for the past three months, the administration said in a statement.

Obama smiled and waved her way through the wrecked centre of Haiti's capital.

After greeting Preval with a kiss at the crushed national palace, she set off with Biden and Haiti's first lady, Elisabeth Debrosse Preval to a post-quake child care centre where 450 boys and girls are participating in art therapy classes in converted city buses donated from Santo Domingo.

Obama jumped, danced and clapped with the singing children. Then the delegation entered one of the green buses for a painting session. Biden made a blue house, Preval a green and yellow sun. Obama painted a purple fish in the ocean.