In a two-hour long television appearance, Hezbollah’s leader, Sheikh Hassan Nasrallah, offered Monday what he contended was evidence proving Israel’s involvement in the assassination of the former Lebanese prime minister, Rafik Hariri, in a 2005 bombing.

The news conference was widely followed in the Arab world, where it was broadcast live by Al-Jazeera, the satellite channel. In Lebanon, it was much anticipated, coming amid speculation that an international tribunal investigating Mr. Hariri’s death would indict members of Hezbollah later this year. Mr. Hariri’s supporters have long contended that Syria or its allies in Lebanon, Hezbollah foremost among them, were behind the killing.

Israel was quick to dismiss the allegation. “The international community, the Arab world, and most importantly, the people of Lebanon all know that these accusations are simply ridiculous,” a senior Israeli official told Reuters.

Mr. Nasrallah’s appearance comes a week after a clash on the Israeli-Lebanese border, in which an Israeli officer, two Lebanese soldiers and a Lebanese journalist were killed.

Mr. Nasrallah presented a series of clips, each several minutes long, of what he said was Israeli surveillance footage intercepted by Hezbollah of roads and places that Mr. Hariri frequented, including the seaside boulevard in Beirut where he was killed.

“Such surveillance generally comes as the first step of the execution of an operation,” Mr. Nasrallah told reporters during the conference via satellite link.

Mr. Nasrallah acknowledged that the images were not conclusive evidence against Israel but noted that the areas surveyed by Israeli reconnaissance planes were not places that Hezbollah members frequent or live in.

“Is this a coincidence after coincidence after coincidence?” he asked.

He also offered a rationale for the killing. “Israel was looking for a way to assassinate Hariri in order to create political chaos that would force Syria to withdraw from Lebanon, and to perpetuate an anti-Syrian atmosphere in the wake of the assassination," he said.

While the news conference may not shift the debate, it was a sophisticated presentation, and it demonstrated that Hezbollah was able to intercept footage of Israeli aerial reconnaissance. Israel and Hezbollah fought a month-long war in 2006, and many in Lebanon fear that both sides are prepared to fight again.

Tension is running high in the country these days, with fears that the indictments could unleash strife in Lebanon, which remains deeply divided by sect, ideology and the agendas of foreign patrons.