The chief police investigator says that the killers fled the scene after riddling Leal's car with bullets [AFP]

A Guatemalan congressman has been killed in his car within blocks of the legislative assembly where a new president and parliament will take power on Saturday.

Oscar Valentin Leal Caal, who defected this week to the party of the incoming president, was shot dead along with his brother on Friday when two assassins on a motorcycle pulled alongside his gray SUV and pelted the vehicle with at least 17 bullets, police said.

Leal and his brother were outside the headquarters of his current Democratic Freedom Revival party in downtown Guatemala City when the attackers struck.

President-elect Otto Perez Molinaerez told the Prensa Libre newspaper that Leal had been receiving death threats for discussions about joining Perez' conservative Patriotic Party.

Perez, who will be sworn in on Saturday, has vowed to boost the number of police and send the military to fight the Mexican drug cartels who use the country's porous border region as a smuggling route for cocaine.

Crime fighter

Political violence is common in Guatemala and 43 people were killed in the 2011 elections, including municipal and
congressional candidates, according to the office for human rights.

Perez's party won 58 seats in last September's elections to form the largest block in the 158-member unicameral congress, but lacks the two-thirds majority needed to ensure policies pass swiftly.

He has been talking with lawmakers from rival parties to lure them to his party.

Leal, an attorney, had served as a congressman for the Renewed Democratic Liberty party in the last administration.

He was to represent the northern province of Alta Verapaz, where in December 2010 the government declared a 60-day "state of siege" that suspended constitutional rights as state forces raided homes and businesses in search of powerful organised crime bosses.

Chief investigator Fernando Gomez said the killers had fled the scene of the shooting, which also wounded Leal's bodyguard.