Israel was still investigating Saturday's incident, but Hezbollah quickly emerged as the leading suspect because it has an arsenal of sophisticated Iranian weapons and a history of trying to deploy similar aircraft.
The Israeli military said the drone approached Israel's southern Mediterranean coast and flew deep into Israeli airspace before warplanes shot it down about 20 minutes later. Israeli news reports said the drone was not carrying explosives and appeared to be on a reconnaissance mission.
Military officials would not say where the drone originated or who produced it, but they ruled out the Gaza Strip, which is ruled by Hamas, a group not known to possess drones. That left Hezbollah as the most likely culprit and suggested the drone may have flown with the blessing of Iran. Tensions are high between Israel and Iran over Tehran's suspect nuclear program.
"It is an Iranian drone that was launched by Hezbollah," Israeli lawmaker Miri Regev, a former chief spokeswoman for the Israeli military, wrote on her Twitter feed. "Hezbollah and Iran continue to try to collect information in every possible way in order to harm Israel."
She did not offer any further evidence and was not immediately available for comment.
Hezbollah officials would not comment on speculation that the group had launched the drone.
The Israeli dailies Yediot Ahronot and Maariv published maps based on military "estimates" that claimed to show the route taken by the drone.
The maps said the aircraft took off south of the Lebanese coastal city of Sidon, headed south and then turned east over the Gaza Strip and into Israel. Yediot also claimed the drone was made in Iran.
The Israeli military said it began tracking the aircraft over the Mediterranean but waited until it was over an empty, desert area to bring it down in order to avoid casualties on the ground.
Sunday's Israeli air raids, buzzing over pro-Hezbollah villages in southern Lebanon, appeared to be aimed at reminding the guerrilla group of Israel's air superiority.
At times of heightened tensions, the Israeli air force often carries out mock raids over Lebanese territory. Israel has U.S.-made F-15 and F-16 warplanes, but it was not clear exactly what type of planes were flown Sunday.
Lebanon's national news agency said the planes flew low over the market town of Nabatiyeh and nearby villages.
With a formidable arsenal that rivals that of the Lebanese army, Hezbollah is already under pressure in Lebanon from rivals who accuse it of putting Lebanon at risk of getting sucked into regional turmoil. Confirmation that Hezbollah was behind the drone would put the group under further strain internally.
Hezbollah, a powerful Shiite group committed to Israel's destruction, has long served as an Iranian proxy along Israel's northern border. The two sides fought a brutal, monthlong war in mid-2006. Hundreds of people were killed, and Hezbollah fired several thousand rockets and missiles into Israel before the conflict ended in a stalemate.
Hezbollah has attempted to send unmanned aerial vehicles into Israel on several occasions dating back to 2004. Its leader, Sheik Hassan Nasrallah, has claimed that the group's pilotless aircraft were capable of carrying explosives and striking deep into Israel. The last known attempt by Hezbollah to use a drone took place during the 2006 war, when Israel shot down an Iranian-made pilotless aircraft that entered Israeli airspace.
Since the fighting ended, the sides have been locked in a covert battle against one another.
"The war between Hezbollah and Israel was not extinguished at any moment, be it in the media or at the intelligence level," said Ibrahim Bayram, an expert on Shiite affairs who often writes about Hezbollah for Lebanon's An-Nahar newspaper.
"Israel is always trying to breach Hezbollah's security and in return Hezbollah is also working day and night to breach Israel's security," he added.
Hezbollah has accused Israel of assassinating a top Hezbollah operative in 2008 in Syria. The group and Lebanese officials say they have broken up several Israeli spy rings inside Lebanon over the past few years.
Israel, meanwhile, believes Hezbollah, with Iranian backing, is behind a string of attempted attacks on Israeli diplomatic targets in India, Thailand and the former Soviet republic of Georgia, plus a deadly bombing earlier this year that killed five Israeli tourists in a Bulgarian resort. Last week, Israel announced the arrest of an Arab citizen it accused of spying for Hezbollah, the latest in a string of such cases.
Many speculated that the aircraft was trying to gather intelligence on Israel's secretive nuclear reactor in the southern desert town of Dimona. Foreign experts believe the facility houses an arsenal of nuclear weapons, a claim that Israel neither confirms nor denies.
"It's quite a long distance, indicating a high level of sophistication," said Shlomo Brom, a retired Israeli general who is now an analyst at the Institute for National Security Studies, an Israeli think tank.
The drone flight also came against the broader backdrop of rising tensions between Israel and Iran.
Israel accuses Iran of trying to develop nuclear weapons, which it believes would threaten its existence, given the repeated calls by Iranian leaders for the destruction of Israel. Iran insists its nuclear program is for peaceful purposes only.
Israeli leaders have repeatedly held out the possibility of attacking Iranian nuclear facilities if they conclude that international sanctions and diplomacy have failed to curb the Iranian program.
Iran, in turn, has threatened to retaliate if it is attacked, raising the possibility of Hezbollah unleashing more rockets and missiles into Israel. Hezbollah has not said how it will react to an Israeli attack on its benefactor.
Iran recently claimed it now has drones capable of carrying missiles as far as 2,000 kilometers, or 1,250 miles, putting much of the Middle East, including Israel, within distance. The aircraft appeared to be similar to the American RQ-170 Sentinel, one of which went down in Iranian territory last year. Iran said it was building a copy of the RQ-170 in April.
Iran frequently makes announcements about its strides in military technology, but it is virtually impossible to independently determine the capabilities of its weapons.
Yiftah Shapir, another analyst at the INSS, said Saturday's incident may have been meant as a warning to Israel.
"The drone could be a message that they have the capability to pull this off, and do so perhaps with weapons," he said.
He said Israel likely allowed the drone to fly so far into its airspace, instead of shooting it over the sea, in order to analyze its capabilities before taking it down.
Federman reported from Jerusalem. Lauren E. Bohn in Jerusalem contributed to this report.