"For the first time, I can say that we have advanced positively in the negotiations concerning the two Israeli soldiers and [Lebanese] prisoners," Nasrallah said.
"I assert that there are strenuous negotiations, continuing sessions which will be resumed in days," he said.
Nasrallah did not actually say whether the soldiers were still alive. Israeli government officials declined to immediately comment on Hezbollah's assertion, saying they would have to study the speech first.
The manner of the exchange on Monday between Israel and Hezbollah was criticised by Samir Geagea, head of the executive authority in the Lebanese Forces party, which is part of Lebanon's ruling March 14 coalition.
He said that the Lebanese government should have been aware of the deal.
"My first comment is about the Israeli national who arrived in the Lebanese coasts in 2005 ... Why did Hezbollah not inform the Lebanese authorities of that?" Geagea said.
"Second, this prisoner swap deal took place away from the Lebanese state."
Earlier on Tuesday, Ehud Olmert, the Israeli prime minister, said the return of the two Israeli soldiers captured by Hezbollah last July is still far off.
Olmert's comments dashed hopes that the swap a day earlier would pave the way for further exchanges.
Hezbollah's capture of two Israeli soldiers in July 2006, sparked a 34-day war between the Lebanese group and Israel, leaving about 1,400 people dead.
Israel failed to win the freedom for its soldiers.
Hezbollah has repeatedly said it would only exchange the two soldiers against the release of all Lebanese and Arabs detained in Israel.
Negotiations are being mediated by the UN.