Thousands of security personnel and high-tech surveillance systems dotted every nook and corner of this Turkish resort town as leaders of the world's 20 top economies, including Prime Minister Narendra Modi, congregated here for the two-day G20 Summit beginning on Sunday. The heightened security measures, comprising of over 12,000 security personnel, drone detection equipment, 350 mobile cameras with licence-plate recording and face-recognition systems, follow the audacious terror attacks in Paris Friday night. Markets and shops around the venue have been shut and thousands of barricades and security personnel are deployed on alongside roads leading to the venue. As part of additional security measures, no tourists are allowed to stay in the hotels in Belek for the entire duration of the summit, which ends on Monday. At least 30 of the 46 hotels in the area have been designated as part of the summit zone. All these hotels have been equipped with bulletproof glass. The Turkish military has put in place an around-the-clock air defence system to prevent any possible missile or drone attacks. Officials said more than 350 mobile cameras with license-plate recording and face-recognition systems have been installed on the highway from Antalya airport to the seaside enclave and around the hotels where world leaders including US President Barack Obama and Russian President Vladimir Putin are staying. Two indoor sports stadiums in Antalya have been turned into temporary police stations and one of the international arrivals terminals within the Antalya Airport has been allocated for G20 participants. Due to security concerns, visiting delegations are not disclosing where their officials will stay during the summit. All the world leaders, including Prime Minister Modi, have condemned the Paris attacks. French President Francois Hollande cancelled his visit on Saturday due to the tragedy. Modi arrived here last night from London after his three-day UK visit. Those having arrived also include Saudi King Salman bin Abdulaziz Al Saud, whose entourage included 65 Mercedes-Benz vehicles. The UN secretary general Ban Ki-moon and the heads of the International Monetary Fund (IMF), the World Bank and other international organizations will also be present at the summit. The G20 is made up of 19 countries and the EU. This year, six more countries have been invited as guests. The summit was estimated to have added $214 million to the Turkish economy, according to local media reports.