Zimbabwe's main opposition Movement for Democratic Change (MDC) said on Wednesday it has filed petitions with the Electoral Court challenging results in 13 out of the 78 constituencies won by the ruling party in the March 31 parliamentary election.

It had 14 working days from the date of the election or until Thursday this week to file the petitions.

Party spokesperson, Paul Themba-Nyathi, said his party had filed 13 petitions as a test case to show how the elections were rigged.

Most observer groups to the election, including those from the Southern African Development Community (SADC) and the South African government, have declared it free and fair and the best conducted in the country and the region so far.

For the first time in Zimbabwe, the elections were held in accordance with the SADC Guidelines on democratic elections, which saw a number of changes introduced to the electoral system in the country.

These included voting in one day, counting at polling stations, use of translucent ballot boxes and use of visible and indelible ink.

Analysts have however questioned why the MDC is not disputing results of those constituencies where it won. The ruling Zimbabwe African National Union-Patriotic Front won 78 of the 120 contested parliamentary seats, up from 61 in 2000 while the MDC won 41, down from 57 in 2000.