UNITED NATIONS (REUTERS) - Russia has amassed tens of thousands of well-equipped troops near the Ukrainian border in addition to the 25,000 troops it recently moved into Crimea, Britain's UN ambassador said on Sunday.

"Satellite images show that there are between 35,000 and 40,000 Russian troops in the vicinity of the border with Ukraine equipped with combat aircraft, tanks, artillery and logistical support units," Ambassador Mark Lyall Grant said.

"This is in addition to the 25,000 Russia troops based illegally in Crimea" which Russia seized last month, Mr Grant said.

He was speaking during an emergency meeting of the UN Security Council on Ukraine.