LIMA (Reuters) - Peruvian President Pedro Pablo Kuczynski said on Thursday that authorities leading an expanding graft investigation into Brazilian builder Odebrecht had gone too far by raiding the offices of the rightwing opposition party that rules Congress.

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The attorney general’s office has spent the past year working to identify the recipients of bribes that Odebrecht has admitted paying to secure contracts over a decade-long period in Peru, one of a dozen nations where it has acknowledged crimes.

After entangling two former presidents this year, the investigation has gathered steam again in recent weeks, with four executives of local construction companies jailed pending trial and a former mayor named as a suspect.

On Thursday, prosecutors investigating Odebrecht’s financing of political campaigns searched the offices of the rightwing opposition party Popular Force, prompting party representatives to accuse the attorney general’s office of political bias.

In a rare gesture of sympathy for a party that often attacks him, Kuczynski called for prosecutors and other state authorities to “respect the rules of the game.”

“It worries me to read the news about a raid this morning on the Lima offices of the political party that dominates Congress. And I’m not saying this to ingratiate myself with Congress. I’m saying this because if there isn’t respect for due process, we won’t be respected internationally,” Kuczynski said in a televised speech at an event with local mayors.

Kuczynski’s remarks come as Popular Force is preparing legislation to oust Attorney General Pablo Sanchez, who has repeatedly denied political bias and said his office was only working to fight corruption and impunity. Sanchez did not immediately respond to requests for comment.

The raids at the offices of Popular Force were authorized by Judge Richard Concepcion, who earlier this year ordered ex-Presidents Ollanta Humala and Alejandro Toledo to be held in pre-trial detention while prosecutors prepare criminal charges.

“This is an affront to the party,” Popular Force Secretary General Jose Chlimper told reporters in front of one of the party’s offices as prosecutors worked inside. “They’re looking for something that they’re not going to find.”

Popular Force’s leader, twice-defeated presidential candidate Keiko Fujimori, is under investigation for allegedly laundering money for Odebrecht during her 2011 campaign, which she has repeatedly denied.

In recent weeks, Popular Force lawmakers have criticized Kuczynski for declining to undergo questioning in Congress after local media reported he worked for Odebrecht as a consultant. Kuczynski has denied the allegations and sent written responses to lawmakers’ questions.