Amritsar, Jan 17 (ANI): Security has been tightened across India ahead of Republic Day's celebrations on January 26. Extra vigil is being mounted at border towns as Indian security agencies fear militant attacks from across the border ahead of US President Barack Obama's visit to the country. Obama will be the first US President to attend a Republic Day celebration. He is the only US President to visit the country twice while in office. India security officials have said around 200 militants are waiting to cross over from across the border.