Balloting is taking place at 30,574 polling booths across 10 districts of Telangana including Hyderabad.
More than 28.17 million electors are eligible to exercise their franchise in the first election in Telangana since parliament passed a bill in February for separate statehood to the region.
As many as 265 candidates are in the fray for the Lok Sabha and 1,669 for the assembly constituencies.
Technical snag in Electronic Voting Machines (EVMs) led to delay in start of the polling at some polling centres.
17 Lok Sabha and 119 assembly constituencies went to polls
Chief Electoral Officer (CEO) Bhanwarlal told reporters that some EVMs received from Electronic Corporation of India Limited (ECIL), Hyderabad were in factory mode and the polling staff was unable to use them.
He, however, said such EVMs were being replaced in 20 minutes to half-an-hour as every district has 2,000 EVMs in reserve.
"There is a small technical snag in new EVMs. They are in factory mode and they have to be sent back to the factory but we have sufficient number of machines for immediate replacement," he said.
The election authorities are using 100,000 EVMs. The CEO said these were new machines which arrived two days ago from ECIL and Bharat Electronics Limited (BEL).
Polling, which began at 7 a.m., will continue till 6 p.m. in 109 assembly constituencies. In 10 Maoist affected constituencies, polling will end at 5 p.m. while in three other segments the deadline is 4 p.m.
Director General of Police B. Prasada Rao said the polling was on in a peaceful manner. He said no untoward incident was reported from any part of Telangana.
The CEO said 150,000 security personnel including paramilitary forces were deployed as part of the massive security arrangements. Four helicopters were also kept ready for contingency.
Prominent among the contestants for Lok Sabha elections include union cabinet Minister S. Jaipal Reddy (Mahabubnagar), Telangana Rashtra Samithi (TRS) chief K. Chandrasekhara Rao (Medak), his daughter K. Kavitha (Nizamabad), Lok Satta chief Jayaprakash Narayan (Malkajgiri) and Majlis-e-Ittehadul Muslimeen (MIM) president Asaduddin Owaisi (Hyderabad).
As the state will be formally bifurcated in June, the Election Commission is conducting the polls in the undivided state.
The elected legislators will be allotted to the respective states after June 2.