The counting was taken up at 13 centres in the 12 districts in which the constituencies are situated.
Elaborate security have been made with the deployment of a 9,000-strong force at the counting centres.
The polling was held on June 12.
Bypolls to 16 of the 18 Assembly constituencies were necessitated as sitting Congress MLAs were disqualified by the Assembly Speaker for switching loyalty to YSR Congress chief Jaganmohan Reddy and voting against the Congress government during a no-trust vote in December.
Also, actor-turned-politician Chiranjeevi resigned as MLA following his election to Rajya Sabha that caused bypoll in another seat.
The sitting Congress MP quit in support of Jagan which necessitated by-election for Lok Sabha constituency in Nellore.
The outcome of the by-elections is expected to impact the YSR Congress as the performance would decide the party's hopes to grab power in the 2014 Assembly elections.
The results are equally important for the ruling Congress as a poor performance might lead to more defections of its MLAs to Jagan's party, thus affecting the stability of the government.
Two Congress MLAs had shifted their loyalty to the Kadapa MP soon after his arrest last month in an alleged disproportionate assets case.
The bypolls are also significant for main Opposition Telugu Desam, as a poor show would demoralise its ranks in the run up to the 2014 elections.
