The IEC also says it has begun an audit of the results of the election, after opposition parties contested preliminary results that look set to give the ruling party a landslide victory.
The Basotho National Party (BNP), which has the second largest number of votes, has threatened to boycott parliament.
In the last parliamentary poll four years ago, the LCD won a massive landslide, but the BNP refused to accept the result, and months of political crisis ensued.
A new electoral system was used this time which was intended to produce a more representative parliament.
'Free and fair'
In addition to 80 seats elected on a first-past-the-post basis, 40 seats will be allocated according to the share of votes each party receives nationally.
The only seat which has not gone to the LCD so far was won by the Lesotho People's Congress in the capital, Maseru.
Many people expected Lesotho's general election to be close, but as the results trickle in from around the country, the BBC's Richard Lee in Maseru says it is becoming increasingly clear that the ruling LCD is heading for another comprehensive victory.
"It's going to be a one-party parliament all over again... If the LCD goes to parliament unopposed, we will not participate in that parliament," the leader of the BNP, Major-General Justin Lekhanya, told Reuters news agency.
Observers, including delegations from southern Africa, Japan, Europe and the United States, have issued statements declaring that the election was free, fair and transparent.
But the BNP is not convinced, and an audit has begun.
"Political parties will be invited to participate in and have access to the information from this audit," IEC chairman Leshele Thoahlane said in a statement.
Mountains
Turn-out was high, with more than 70% of the 830,000 registered voters casting their ballots, according to the IEC.
Lesotho experienced months of instability following the 1998 poll, which culminated in a military intervention by troops from South Africa and Botswana.
This year, all the parties signed an electoral code of conduct committing themselves to respect the results.
Hopes that provisional results could be released on Monday evening have been dashed as the ballots in some polling stations in remote mountain areas will be collected by helicopter only on Tuesday.
Final results will be issued on Thursday, IEC chairman Leshele Thoahlane said.