"What we are looking at is possible record turnout," he said.
"You have the sense here that people really felt like their vote was going to count for the first time in a long time."
It is the first time that a Lebanese election has been held on a single day rather than over a month.
Some polls have forecast a narrow victory for Hezbollah and its allies, including the Free Patriotic Movement, headed by Michel Aoun, a Christian leader and former military chief.
But most analysts believe that Lebanon's complex political system will lead to a unity government including elements of the March 14 bloc, which currently holds the parliamentary majority.
The country's president must be a Maronite Christian, the prime minister a Sunni Muslim and the speaker of parliament a Shia Muslim.
The 128 seats in parliament are divided equally between Christians and Muslims.
The US, which lists Hezbollah as a "terrorist" group, has linked future aid to Lebanon to the shape and policies of the next government.
"The challenge will be to bring winners and losers together, rather than exacerbate their differences and threaten to trigger another cycle of violent confrontation," an International Crisis Group report, released before polling day, said.
The elections look likely to be decided largely by Lebanon's divided Christian districts.
Aoun faces Christian rivals in the shape of the Phalange party led by Amin Gemayel, a former president, and the Lebanese Forces led by Samir Geagea, both members of the March 14 camp.
Al Jazeera's James Bays, reporting from Lebanon, said that the Christians appeared set to emerge as the "kingmakers".
"To put it simply, the Christians are bitterly divided. The Christians find themselves in the two different camps - there are Christian parties on both sides of the political divide," he said.
"They are the fluid voters that might go either way. So the Christians are going to end up - even though they're very divided - as the kingmakers."
Christians make up nearly 40 per cent of Lebanon's 3.26 million eligible voters.
Security was tight on polling day with more than 50,000 soldiers and police deployed across the country.
Michel Sleiman, Lebanon's president, urged people to vote "calmly and with joy".
"Democracy is a blessing we must preserve, a blessing that distinguishes Lebanon in the Middle East," he said after voting in his home town of Amchit, north of Beirut.
In the run-up to the elections, much of the campaigning has focused on Hezbollah's military power, which is stronger than the state's security forces.
Opponents say Hezbollah's weapons undermine the state, while the group and its allies see them as crucial to defending Lebanon from Israel.
Sectarian tension brought Lebanon to the brink of civil war last year when more than 100 people were killed in violence before an agreement led to the election of Sleiman, then the army chief, as president and the formation of a national unity government.
Polls are due to close at 7pm local time (16:00 GMT).