Bombs have exploded at Mexico's top electoral court, an opposition party's headquarters and a bank in the capital.

The explosions blew out windows and caused other structural damage but no one was injured.

At a branch of Canada's Scotiabank in the south of Mexico City, the explosion tore apart the metal and glass facade of the bank.

In the headquarters of the Institutional Revolutionary Party, the PRI, ceiling panels at a back entrance lie shattered on the floor.

Houses close to the electoral court, known as the Trife, were also damaged in the blast. The concrete court building suffered little damage.

A fourth bomb in a rucksack at another bank was deactivated by police.

The electoral court angered leftists in September by ruling that conservative candidate Felipe Calderon had won July's presidential election fairly.

Judges threw out claims of fraud by leftist candidate Andres Manuel Lopez Obrador, who lost narrowly.

Mr Calderon is to take office on 1 December.

The PRI, which ruled Mexico for 71 years until President Vicente Fox beat it at elections in 2000, is now the third force in Mexican politics.