Five U.S. Marines on Tuesday denied raping a Filipino woman, with two of them saying they were not even present when the alleged assault happened, according to statements filed before prosecutors.

A lawyer for a sixth Marine refused to answer the complaint filed by the 22-year-old woman, saying his client could not respond to "piecemeal" submission of statements and evidence by the complainant and witnesses.

The woman claimed she was raped by the Marines, who had recently taken part in a counterterrorism exercise in the northern Philippines, inside a van at Subic Bay free port, a former U.S. Naval base northwest of Manila.

The driver was first considered a key witness but in television and radio interviews later he said he was punched twice by an investigator to force him to sign a statement saying the woman was gang-raped by the Marines.

"I categorically deny the allegation that I along with the other Marines in the van gang-raped [the] complainant," Staff Sgt. Chad Brian Carpentier said in a sworn statement submitted by his lawyer before prosecutors investigating the case.

"No such crime occurred," said Carpentier, who identified himself as a platoon leader of the five other Americans from the 31st Marine Expeditionary unit based in Okinawa, Japan.

Another Marine, Lance Cpl. Dominic Duplantis, said he did not witness a gang rape in the van or any sign of struggle from the complainant, who sat beside fellow Marine Lance Cpl. Daniel Smith on the rearmost seat.

The Marines, who have not been charged, did not attend the preliminary hearing in Olongapo city, west of Manila, where 100 protesters demanded an end to U.S. counterterrorism exercises in the Philippines and the scrapping of an agreement that allows American forces to train in the country.

The Marines have been in the hands of the U.S. Embassy since the alleged rape, and the U.S. government hasn't said if they will be transferred to Philippine custody.

Prosecutor Prudencio Jalandoni said the Marine who refused to hand in his sworn statement by Tuesday's deadline could be indicted "for his failure to rebut the charges."

After receiving statements from the five Marines, complainant and witnesses, Jalandoni said he was confident of reaching a decision on whether to bring charges against the Americans "definitely before Christmas."

The alleged rape has stirred emotions in the former American colony and has been regarded by some as a black mark on U.S. counterterrorism training, which has been credited by Washington and Manila for helping Filipino troops crush many Muslim militants in the country's south.