SINGAPORE - Singapore President Madam Halimah Yacob and Prime Minister Lee Hsien Loong have written letters to their Russian counterparts to convey their condolences over the crash of a Saratov Airlines plane near the Moscow Region on Sunday (Feb 11).

In her letter to Russian President Vladimir Putin, Madam Halimah wrote: "I am deeply saddened to learn of the crash of the Saratov Airlines plane on Feb 11, 2018, and the tragic loss of all passengers and crew on board."

She expressed the people of Singapore's deepest condolences to Mr Putin and the people of Russia. "Our thoughts are with the families of the victims," wrote Madam Halimah.

In his letter to Russian Prime Minister Dmitriy Medvedev, Prime Minister Lee also expressed deepest condolences over the crash.

"Our thoughts are with those affected by this tragedy during this difficult period," wrote Mr Lee.

The Singaporean leaders' letters came as US President Donald Trump called Mr Putin on Monday to offer his condolences over the aerial disaster, reported Agence France-Presse.

Russian officials said Mr Trump and Mr Putin also discussed the Middle East peace process.

Investigators on Monday began examining a black box containing flight data about the Russian passenger place, which crashed near Moscow minutes after take-off, killing all 71 people on board.

Rescuers searched through deep snow for body parts and debris following the disaster, the country's deadliest air crash since 2016.

The Antonov AN-148 plane went down in a snow-covered field, making it difficult to access, with emergency workers forced to reach the wreckage by foot or on snowmobiles.

Russia's Aviation Committee said the black box was recovered from the scene on Monday, adding that "some 400 pieces of the plane" have also been found.