The leader of the Lebanon-based militant group Hezbollah says Israel will not be able to free two captured Israeli soldiers through military action, only through a prisoner exchange. Israeli troops entered Lebanon for the first time in six years after the soldiers were kidnapped by Hezbollah militants early Wednesday

Hezbollah leader Hassan Nasrallah told reporters in Beirut the captured Israeli soldiers are being held in a secure place, far away from the border region where they were nabbed. He warned that Israel will not get them back by using force.

"In any case, any military operation will not lead to the recovering of those captives," he said. "The only possible way is through indirect negotiations and then an exchange."

He says Israel must agree to release some of the Lebanese prisoners it is holding, although he did not say how many.

In Jerusalem, Israeli Prime Minister Ehud Olmert called the abduction "an act of war" and rejected negotiation. He said he holds the Lebanese government responsible for the soldiers' safety.

Mr. Olmert promised the Israeli response would be restrained but "very painful."

Nasrallah said the Israelis will meet fierce resistance, cautioning the new Israeli cabinet members that they should talk to their predecessors about the dangers of military action in Lebanon. But he denied that Hezbollah is trying to provoke a war.

"We do not want escalation in the south," said Nasrallah. "That is not our intention. We do not want to lead Lebanon into war. We do not want to lead the region into war."

But he also said that his group, which the United States considers a terrorist organization, would jump at the chance to capture more Israeli troops.

The Hezbollah chief tacitly acknowledged that some Lebanese factions would not approve of the group's actions, and he made several pointed comments calling for solidarity and cooperation. He called on the Lebanese government to act with what he called "patriotic responsibility."

The Lebanese government has denied any involvement in the abduction of the two Israeli soldiers. It has called for an urgent meeting of the U.N. Security Council to discuss what it calls Israel's "aggressive" response.

The events along the Lebanese-Israeli border have sparked tremendous anxiety in the international community. The U.S., Russia, the European Union and the United Nations have all called for the return of the Israeli soldiers, and also called for restraint in the Israeli response.

The Israeli military is already waging one battle to free a captured Israeli soldier in the Gaza Strip. Now Israel has called up thousands of military reservists to active duty in response to the Hezbollah kidnapping.

It is the first time that ground troops have entered Lebanon in any strength since the Israeli withdrawal from southern Lebanon six years ago. Israeli jets and warships have launched strikes deep into Lebanese territory, taking out several bridges and virtually sealing off the southern region.

The Israeli incursion into Lebanon is believed to be the largest since "Operation Grapes of Wrath" a decade ago.