On Tuesday, Guatemala's Constitutional Court rejected President Otto Perez's appeal for presidential immunity that also sought to legally erase a pre-trial investigation of graft allegations.
On Friday, a Congressional committee recommended fully lifting that immunity and allowing the investigation to proceed.
Protesters last night shouted "Out with Otto Perez" and "No more corruption" as they marched from the Supreme Court to the National Palace in the city's historic centre.
Holding candles and flaming torches, many carried multi- coloured banners with slogans such as: "With Otto Perez's government, corruption and repression increase."
The probe against Perez was requested by opposition party Winaq after a UN-backed investigation aimed at cleaning up the Guatemalan judicial system reported in April that senior customs officials had taken bribes from businessmen seeking to avoid paying taxes.
The main suspect in the fraud, Juan Carlos Monzon, an aide to the vice president, is now a fugitive from the law.
In a separate scandal, the president of the central bank and the director of the social security system -- both of whom are close to Perez -- were arrested in May on charges of cheating the social security system out of approximately USD 15 million.
"We live with much injustice in Guatemala, the governments are complicit in corruption," Oscar Farfan, a 40-year-old protester who joined the march after walking 45 kilometres from the western indigenous town of Sumpango, told AFP.
