Reports from Antarctica say a Chinese icebreaker and a Russian research vessel broke free from thick ice on Tuesday, with both vessels moving toward open waters.

China's official Xinhua news agency, reporting from on board the Xue Long, said the ship reached open waters late Tuesday Beijing time after spending nearly a week icebound. The breaker became trapped and isolated after using one of its helicopters to rescue passengers from the stranded Russian research ship Akademik Shokalskiy.

The Russian vessel left New Zealand November 28 in an attempt to recreate Australian explorer Douglas Mawson's century-old voyage to Antarctica, before getting stuck December 24. The Chinese breaker got stuck after rescuing the Russian vessel's 52 passengers.

Authorities said late Tuesday the services of U.S. Coast Guard ice breaker Polar Star, dispatched earlier this week to help, were no longer needed. The ship will now continue on its original resupply mission to a key U.S. base on the frozen continent.