MEXICO CITY (AFP) - Packed with sightseers eagerly snapping pictures on their cameras and mobile phones, this looks like any other tour bus in the world - or almost.

In fact, the converted school bus with the sawed-off top is taking Mexico City visitors on the "Corruptour", a visit to the country's seedy underbelly of murderous misdeeds and multibillion-dollar graft by public officials.

Stops include a scandal-plagued subway line that cost more than $1 billion, and an impromptu "anti-monument" to the 43 students abducted by corrupt police and feared massacred in the southern state of Guerrero.

Organisers also wanted to include a stop at the "White House" - the sumptuous house that First Lady Angelica Rivera bought in an alleged sweetheart deal with a government contractor - but reluctantly concluded it was too far, given the capital city's notorious traffic.

The gray tour bus, which features a blood-red Corruptour logo in horror-film style type, made its debut journey Sunday.

Organisers plan two tours every Sunday afternoon, free of charge, leaving from Mexico City's iconic Chapultepec Park.

It is the culmination of a yearlong effort, said organizer Patricia de Obeso.

"We want people to get informed about this issue in a fun way and spark ideas to overcome corruption," she said.

"But just because it's fun doesn't mean (the crimes) aren't serious and documented," added fellow organizer Miguel Pulido on the website corruptour.mx.

The 27 sights include a stop on the number 12 subway line, which cost 24.5 billion pesos ($1.7 billion) and had to be shut for emergency repairs in 2014, just two years after it opened.

The shiny local headquarters of Spanish construction group Obrascon Huarte Lain (OHL) - accused of massive corruption on government contracts - is also on the menu.

"One of Mexico's main problems is corruption and bringing it to justice. Abusers aren't always punished," said human rights specialist Miguel Moguel, who was along for the inaugural tour.

"It was a very rewarding experience. You realize that there's a group of citizens - maybe like a lot of others in the country - that's trying to change things," said 18-year-old student Adrian Emigdio.

Watchdog group Transparency International ranks Mexico 123rd out of 176 countries in its latest index of corruption worldwide.