* Russia retains very capable force on border-NATO commander
* Kremlin said Putin ordered troops to withdraw to bases
* NATO chief Stoltenberg on first visit to military HQ (Adds more quotes from NATO officials)
By Adrian Croft
MONS, Belgium, Oct 24 (Reuters) - Russia still has troops in eastern Ukraine and retains a very capable force on the border despite a partial withdrawal, NATO's military commander said on Friday.
"We've seen a pretty good withdrawal of the Russian forces from inside Ukraine but, make no mistake, there remain Russian forces inside eastern Ukraine," U.S. Air Force General Philip Breedlove told reporters at NATO's military headquarters near Mons in Belgium.
Some Russian troops stationed near the Ukraine border had left and others appeared to be preparing to leave.
"But the force that remains and shows no indications of leaving is still a very, very capable force," said Breedlove, NATO's supreme allied commander Europe.
The presence of a "large coercive force" on the Ukraine border was not helpful to progress in implementing the Minsk agreement, he said, referring to a ceasefire agreement between Ukraine and pro-Russian rebels reached in the Belarussian capital last month.
"We would call for the complete withdrawal of Russian forces from inside of Ukraine and the withdrawal of all the forces on the border back to garrison," he said.
A day before the Minsk accord, NATO said Russia had several thousand combat troops inside Ukraine, as well as around 20,000 troops close to the border. Breedlove gave no figures on Friday.
The Kremlin said on Oct. 12 that President Vladimir Putin has ordered Russian troops to withdraw to their permanent bases after military exercises near the Ukraine border. Russia has denied having troops inside Ukraine.
Dutch Brigadier-General Nico Tak, director of NATO's crisis operations center at Mons, said Russia was "in a position to reinforce their forces inside Ukraine at a moment's notice" and he said the Ukraine ceasefire was being violated all the time.
BEEFING UP DEFENSES
NATO has suspended practical cooperation with Russia in protest against Moscow's annexation of Crimea and its support for the pro-Russian separatists in eastern Ukraine.
NATO leaders have said the alliance has no plans to intervene militarily in Ukraine, which is not a NATO member. But they have beefed up NATO's eastern defenses to reassure nervous allies.
NATO Secretary-General Jens Stoltenberg, making his first visit to NATO's military headquarters since he took over at the start of this month, said Russia remained in violation of international law in Ukraine.
"They are still violating the sovereignty and the territorial integrity of Ukraine by having Russian forces in Ukraine," the former Norwegian prime minister told reporters while visiting the NATO crisis operations center.
Stoltenberg said Sunday's Ukraine election would be an important step to show that Ukraine was a stable, democratic society and he urged everyone to respect the results.
President Petro Poroshenko is seeking a mandate in Sunday's vote to press ahead with his plan to end the separatist conflict and pursue integration with mainstream Europe.
Stoltenberg urged Russia to use its influence to make sure the ceasefire in eastern Ukraine was respected. "We need to find a political solution to the challenges we see in Ukraine and a pre-condition for that is of course to have an effective ceasefire," he said.
Asked about Sweden's search for a suspected foreign submarine, Breedlove said: "We've seen increased Russian activity...in the air, on the sea, and on the land, so certainly these kind of issues are not unexpected."
Breedlove declined comment on whether he believed the suspected mystery vessel to be a Russian submarine, saying he had not yet received specific information from Sweden.
The Swedish military said on Friday that it had called of its search. (Editing by Angus MacSwan)