The guerrillas accused para-military forces supported by the Sri Lankan army of kidnapping 10 aid workers of the Tamil Rehabilitation Organization or TRO, and said the abductions made it "difficult to resume talks," with the government expected to take place in Geneva, later this month.
The TRO is a registered charity in Sri Lanka, believed to have strong links to the Tigers.
"There has been some miscommunication. The two girls had returned home Monday, but were afraid to report anything due to threats to their lives from the abductors," said Arjunan Ethirveerasingam, of the Tamil Rehabilitation Organization. "We still haven't head anything from the others," he said, about the eight other aid workers who remained missing.
He said it wasn't immediately known if the two female workers had been released or had escaped, adding that they were being questioned.
The two separate alleged abductions had taken place on Sunday and Monday close to the Welikanda army check point in restive eastern Batticaloa, about 150 kilometers from the capital Colombo, Ethiriveerasingham said.
The government and the military refuted the charge. "The government categorically denies any such incident taking place in close proximity to the Walikanda checkpoint," the governments said in a statement.
"This is a fabricated story against the security forces," said Brig. Prasad Samarasinghe, military spokesman. He said the location the TRO alleges the abductions took place was a populated area and someone would have witnessed the incident, which however was not the case.
However, the alleged incidents that raised international concern, also worried the government about its effect on proposed talks with the Tigers. Some speculated meanwhile, that the alleged abductions were aimed at whipping up international sentiment against the government and for the Tigers to squeeze out of the Geneva talks.
The Tigers' threat on Tuesday came barely a week after Norway's top peace envoy Erik Solheim broke an almost three year deadlock to resume stalled peace talks between the government and the guerrillas amid fears that the island was on the brink of war.
The Tigers have been fighting for a separate state since 1983 for the island's ethnic Tamil minority, claiming discrimination by the Sinhalese majority. Nearly 65,000 people were killed before Norway brokered a truce in February 2002. Subsequent peace talks broke down a year later amid rebel demands for wide autonomy in the Tamil-majority north and east.