Ukrainian marines departed Crimea on buses Tuesday, leaving the eastern port of Feodosia without firing a shot as pro-Kremlin soldiers took over the last ships and bases once controlled by Ukraine's forces.

Their exit came as Ukraine's acting defence minister Igor Tenyukh resigned amid harsh criticism for authorities' often-hesitant reaction to Russia's largely bloodless occupation of Crimea. In an emotional speech in parliament, the outgoing defence chief rejected criticisms that his handling of the crisis was too indecisive and that Ukrainian troops were not given clear instructions.

Kyiv considers Moscow's annexation of Crimea illegal, but ordered its troops to leave the Black Sea peninsula for their safety on Monday. So far, 131 marines have left, according to the defence ministry.

Tenyukh's resignation was eventually accepted by parliament after lawmakers initially refused. Col. Gen. Mikhail Kovalyov was appointed as Tenyukh's replacement.

About 4,300 Ukrainian servicemen and 2,200 of their relatives have asked to leave Crimea, Tenyukh said Tuesday. That means about two-thirds of the 18,800 military personnel and relatives that he said were stationed on the Black Sea peninsula were so far taking their chances in Crimea.

Obama threatens more sanctions

It was not clear how many of those troops had joined the Russian army or had simply demobilized.

Canada to continue Ukraine talks

Canadian Prime Minister Stephen Harper is set to remain in Europe to spend two days in Germany meeting with Chancellor Angela Merkel.

The two most senior members of the G7 are expected to discuss the ongoing crisis in Ukraine.

Harper will travel to Munich and Berlin during his time in Germany.

Meanwhile, U.S. President Barack Obama said Tuesday that Russia will face sanctions designed to harm specific economic sectors if it fails to de-escalate the situation in Ukraine.

Obama, speaking at the end of the nuclear security summit at The Hague, Netherlands, said the sanctions could target Russia’s energy, finance, arm sales and trade sectors.

“We are prepared to take the next step if the situation gets worse,” Obama said.

Potential sectoral sanctions are still being researched, Obama said. Prime Minister Mark Rutte of the Netherlands, standing at a podium alongside Obama, said European countries support the U.S. idea, even though the new sanctions would have global financial repercussions.

"These sanctions would hit Russia very badly," Rutte said.

“And obviously, you can never guarantee that the people in Europe, in Canada, in the U.S. would not be hurt," he added. "But obviously, we will make sure that we will design these sanctions in such a way that they will have maximum impact on the Russian economy."

Obama conceded Russia has a right to station 30,000 of its troops near the eastern Ukrainian border, but urged Vladimir Putin’s government to seek a diplomatic solution with Ukraine.

'We are prepared to take the next step if the situation gets worse'- U.S. President Barack Obama

“This is not a zero sum game,” Obama said, adding there was a place for Russia’s influence in Ukraine.

“It is up to the Ukrainian people to make decisions about how they organize themselves and who they interact with."

Obama stood fast on his insistence that Crimea remains a part of Ukraine, even as the fledgling Ukrainian government in Kyiv ordered its troops to pull back from the disputed territory.

NETHERLANDS-NUCLEARSUMMIT/ Obama Ban Ki-moon

UN Secretary-General Ban Ki-moon and U.S. President Barack Obama share a word during the Nuclear Security Summit in The Hague on Tuesday, where the Ukraine crisis overshadowed the normal agenda. (Doug Mills/Reuters)

"We're not recognizing what is happening in Crimea," Obama said at his first news conference since Russia moved to annex Crimea after a referendum 10 days ago. Obama rejected "the notion that a referendum sloppily organized over the course of two weeks" would "somehow be a valid process."

Obama said he didn't think international recognition of Crimea as part of Russia is "a done deal." But he also said, "It would be dishonest to suggest there is a simple solution to what has already taken place in Crimea," where Russia troops are in control.

Russia booted from G8

Side discussions about Ukraine have overshadowed some of the summit's nuclear agenda. On Wednesday, G7 leaders issued a declaration reiterating their support for Ukraine’s new government and calling Russia’s annexation of Crimea illegal.  

​The leaders “reaffirm our support for Ukraine's sovereignty, territorial integrity and independence,” the declaration read.

The G7 countries — Canada, France, Germany, Italy, Japan, the U.K. and U.S. — have suspended what's normally the G8 due to Russia's actions, and have cancelled an upcoming summit set to be held in Sochi. 

Those actions got only a dismissive reaction from Russian Foreign Minister Sergei Lavrov.

"The G8 is an informal club," he said.

"It has no membership tickets, and it can't purge anyone by definition."

The G7 did praise Russia for its decision to allow observers from the Organization for Security and Co-operation in Europe into Ukraine.

Representatives from Ukraine, meanwhile, worked on a deal with the International Monetary Fund to provide a $15-20-billion relief package. 

With files from Reuters, Associated Press, Canadian Press