Quoting diplomatic sources in Beirut and Baghdad, the Lebanese daily newspaper al-Safir reported that Georges Fernando and Jamil Dib were abducted on Monday.
The third, Habib Samur, has been a captive since May. He claimed to be working for a "market research company providing information to the Americans" in Iraq.
The two latest men to be taken captive are believed to have been working for the Soueidan construction firm.
Security sources said the Lebanese envoy to Baghdad, Hasan Hijazi, had told the foreign ministry in Beirut that Monday's captives were in good health.
A group calling itself the Battalian of Islamic Anger released footage of Samur, which was screened by the Dubai-based Al-Arabiya satellite television channel.
In the video Samur was seen stating that he had entered Iraq after US-led forces took over Baghdad in April 2003.
"I would like to appeal to the Lebanese government and all Lebanese leaders to get me out of this awkward situation which I don't know how I came to be in"
But a statement accompanying the video stated that Samur had led a spy cell, most of whose members were Iraqis.
The footage also showed an identity document with a photograph of the detained man which listed him as born in the village of Alma al-Shaab in southern Lebanon.
Dead captive found
"I stress that I am being well treated by the mujahadeen group... I would like to appeal to the Lebanese government and all Lebanese leaders to get me out of this awkward situation which I don't know how I came to be in," said the white-bearded Samur.
However, the body of a fourth Lebanese man, Husain Ulayyan, who worked for a telecoms firm, was found in Baghdad on Sunday.