Ukraine tensions: Joe Biden says US citizens should leave Ukraine now

US President Joe Biden has called on all American citizens remaining in Ukraine to leave the country immediately, citing increased threats of Russian military action.

Mr Biden said he would not send troops to rescue Americans if Moscow invades Ukraine.

He warned that "things could go crazy quickly" in the region.

Russia has repeatedly denied any plans to invade Ukraine despite massing more than 100,000 troops near the border.