Grieving Russians piled flowers high at St Petersburg's Pulkovo Airport on Sunday, mourning more than 200 compatriots who died as they flew home over Egypt, and laid out candles in Moscow to spell out 7K-9268 - the number of the flight that crashed.
The Airbus A321 came down in a mountainous area of central Sinai on Saturday as it carried holidaymakers from the Red Sea resort of Sharm el-Sheikh to St Petersburg, killing all 224 people on board.
President Vladimir Putin declared Sunday a national day of mourning for the victims of the latest in a string of disasters to afflict the Russian aviation industry.
"My wife's classmate died in the plane crash. She was flying for the first time and did not return," St Petersburg resident Yury told Reuters TV, standing by the makeshift memorial in Pulkovo Airport. "It's a nightmare for the whole country. It touched everyone, and it was our duty to come here."
Russian soccer matches began with a minute's silence and the names of the deceased passengers, which are believed to have included 214 Russians, were shown throughout the day on state-run television.
Memorial events took place across the country, with flags flown at half mast. The candles forming the flight number were placed on the steps of Christ the Saviour Cathedral in Moscow.
"It's really a catastrophe," Moscow resident Tatyana said. "I hope that God will accept those who were in the plane for their suffering."
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Chinese President Xi Jinping, Pope Francis and U.S. Secretary of State John Kerry expressed their condolences over the crash, along with many other world leaders.
Russia and other former Soviet republics have poor air safety records, notably on domestic flights. Some accidents have been blamed on the use of ageing aircraft, but industry experts point to other problems, such as poor crew training and lax government controls.
An official of a Moscow-based aviation agency said the Airbus of the Kogalymavia airline broke up in mid-air but stressed it was too early to draw conclusions from this.