(Adds two more political killings)

GUATEMALA CITY, Sept 5 (Reuters) - Right-wing former Guatemalan Gen. Otto Perez Molina and center-left presidential candidate Alvaro Colom are in a dead heat heading into Sunday's election, according to a poll released on Wednesday.

The latest poll numbers came amid more reports of campaign violence. Two activists from Nobel Peace laureate Rigoberta Menchu's flagging election campaign were murdered, a party official said. There have been a rash of killings in the run-up to the vote.

Wenceslao Ayapan and Esmeralda Huyu, a municipal councilor, supporters of Menchu's left-leaning Together for Guatemala party, were shot dead while distributing political leaflets, party secretary Nineth Montenegro said.

Menchu, a defender of Mayan victims of Guatemala's civil war, is in sixth place in opinion polls.

Colom has consistently led political polls, but Perez Molina, an ex-head of military intelligence during the 1960-1996 civil war, has been closing the gap with promises to crack down on rampant crime.

In the latest poll, published in the Prensa Libre newspaper, 31.8 percent of voters said they would vote for Perez Molina, while 31.7 said they would support Colom.

The poll of 1,200 people from Aug. 29 to Wednesday had a margin error of 4.1 percentage points, putting the pair in a statistical tie. The two candidates are likely headed for a run-off vote in November and polls predict a close race.

Perez Molina backs using the army to fight crime by selectively declaring states of emergency and suspending constitutional rights in areas overrun by crime. Guatemala has one of highest murder rates in the world.

Nearly 50 people, 20 of them members of Colom's National Unity for Hope party, have been killed during the bloodiest election campaign since the end of the civil war.

At least six people have been killed from Menchu's campaign, including 46-year-old Clara Luz Lopez who was killed in a spray of bullets last week while driving home.

Some of the killings are attributed to powerful drug gangs seeking to control political parties. Others are blamed on political rivalries or personal vendettas.

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