SHILLONG / AGARTALA, May 16 (TIWN): Voting for by-election to the Tura Lok Sabha constituency in Meghalaya began on Monday amid tight security, an official said.Men and women in large numbers queued up in front of polling stations well before voting opened at 7.00 a.m. in the entire state. Polling will end at 4.00 p.m., said chief electoral officer Frederick Kharkongor. The by-election was necessitated following the demise of former Lok Sabha Speaker Purno A. Sangma on March 4.Sangma's youngest son Conrad K.Sangma is contesting the by-election as National People's Party's (NPP)main candidate in a straight fight against Congress entrant Dikkanchi.D.Shira, wife of Chief Minister Mukul Sangma. Shira is also the sitting legislator in the 60-member House Meghalaya Assembly. The BJP and other Meghalaya-based regional political parties - the United Democratic Party, Garo National Council, Hill State People's Democratic Party are supporting the NPP candidate. The centre has deployed 12 additional companies of central armed police force to ensure smooth conduct of the by-poll in the 24 assembly segments in five districts of the Garo Hills region.