The site, accessible at www.familylinks.icrc.org, is intended to provide contacts for Sri Lankans within the divided country as well as those living abroad, the ICRC said in a statement on Monday.
"Communications between the conflict areas and the rest of the country have been cut off and many families are left without any news from their relatives," it said.
The United Nations estimates that more than 40,000 have fled the resurgence of fighting on the northern Jaffna peninsula, and 170,000 across the entire northeast.
Nordic truce monitors in the country have said that a ceasefire between the government and the rebels of the Liberation Tigers of Tamil Eelam (LTTE) exists only on paper even though at least 1,500 people have been killed in fighting since December when clashes began escalating.
More than 60,000 people have died in three decades of separatist conflict and political talks on ending the violence have been on hold since April 2003.