Moscow says the crash of a Russian airbus in Sinai on 31 October, killing all 224 people on board, was the result of a bomb detonated inside the aircraft. Alexander Bortnikov, the head of Russia's Federal Security Service (FSB), told a meeting chaired by President Vladimir Putin on Monday that the plane crash was “unequivocally a terrorist act.” Bortnikov said investigators studied personal belongings, baggage and debris from the aircraft and concluded that an improvised bomb, packed with up to 1.5 kilos of TNT, exploded when the plane was in mid-air. He said traces of explosives were found in the plane's debris. Putin's response was to announce that Russia will intensify air strikes in Syria. “They must be intensified in such a way that the criminals understand that retribution is inevitable,” he said. Putin also ordered Russia's special services to focus on finding those responsible for the atrocity. The FSB is offering a $50 million reward for information leading to the capture of the terrorists. The Interior Ministry has denied, as “completely and totally untrue”, reports that Egyptian authorities have detained 17 people, including two people who are suspected of helping plant the bomb on the plane at Sharm El-Sheikh airport. On Friday evening, Russia's state aviation agency banned Egypt's national carrier, EgyptAir, from flying to Russia after earlier suspending all Russian flights to Egypt. The move followed decisions by Russia and a number of other countries, including Britain, to cancel direct flights to Sharm El-Sheikh. Immediately following the crash, Russian tourist flights to Sharm El-Sheikh continued, only to be halted when it emerged that the sound of what appeared to be an explosion could be heard on the doomed airbus's recovered flight recorder. Russia's biggest airline, Aeroflot, stopped flights from Moscow to Egypt on 18 November. The company said it will not resume flights to Egypt until at least 27 March 2016. Orenburg, an Aeroflot subsidiary, will stop flights to Egypt on 1 December. The 97 Russian companies working in Egypt's tourism sector have investments of $56.5 million, accounting for half of all Russian investments in Egypt. Russians make up close to one in three of all foreign tourists to Egypt. In 2014, three million Russian nationals stayed at Egypt's resorts. The cancellation of flights will have a devastating impact on these numbers. “I understand the reason behind the Russian decision to withdraw its citizens from Sharm El-Sheikh. After all, it was a reaction to the sad death of more than 200 citizens,” said Helmi, a labourer who has lived and worked in Sharm El-Sheikh for decades. “What I fail to comprehend is the decision to ban EgyptAir fights to Moscow. That is a blow to tourism in Sharm and to Egypt as a whole.” “If the cause of the crash was a terrorist act we would expect other countries to support Egypt in its war against terrorism,” said Abu Ahmed, a taxi driver. Instead, he said, there is a blanket ban on flights that will only undermine the economy. A diplomat speaking on condition of anonymity said he appreciated the sentiments of many Egyptians and their frustration at the Russian reaction to the plane crash. He added, “Relations between countries have nothing to do with feelings but are based on communication and understanding.” Which is why, he said, communications between Cairo and Moscow at the most senior level are important if the two nations are to move beyond the crisis. Talks are already underway as the Foreign Ministry and the ministries of tourism and aviation to learn the reasons behind the Russian ban. Foreign Minister Sameh Shukri has been in regular contact with senior Russian officials. This diplomacy became more urgent after Moscow announced that the plane was downed by a bomb. There are growing fears that the Russian disclosure could strain relations between Cairo and Moscow. Tourism Minister Hisham Zaazou says he is also engaged in high-level communications with Russian authorities to solve the “crisis” that has resulted from the halting of EgyptAir flights to Moscow. Zaazou said his ministry is in constant communication with officials at the Russian Federation's Agency for Tourism and with trip coordinators. Aviation Minister Hassam Kamal issued a statement saying that Egypt had not been officially notified by the Russian authorities of the reasons behind the ban and phone calls are being conducted “on a high level” to clarify the situation. EgyptAir normally operates flights from Cairo to Moscow on Saturdays, Tuesdays and Thursdays. Russia's ambassador to Egypt, Sergei Kerbachenko, told an Egyptian satellite channel that the halt in flights is a temporary security measure.