Ukraine crisis: Moscow 'to help free European observers'
Moscow says it will do all it can to bring about the release of European military observers detained in eastern Ukraine by pro-Russian separatists.
The assurance came as EU diplomats revealed they will meet on Monday to discuss new sanctions against Russia.
Earlier, the G7 group of economic powers agreed to intensify sanctions.
The West accuses Russia of leading a secessionist revolt in Ukraine's east, after it annexed Crimea last month. Moscow denies the allegations.
Rebel militia continue to occupy official buildings in a dozen eastern cities, defying the Ukrainian government in Kiev.
Russia has tens of thousands of troops deployed along its side of the border with Ukraine and has said it would act if its interests were threatened.
Russian Foreign Minister Sergei Lavrov and US Secretary of State John Kerry spoke again on Saturday.
Mr Kerry expressed concern about "provocative" Russian troop movements and "inflammatory rhetoric", US officials said.
For his part, Mr Lavrov said Ukraine should stop its military operations in the south-east, the Russian foreign ministry said.
Negotiators are trying to secure the release of eight international observers who were seized and accused of espionage by pro-Russia gunmen.
The observers were taking part in a mission linked to the Organisation for Security and Co-operation in Europe (OSCE).
Quoting German government sources, Reuters said an OSCE team was on its way to the region to try to secure their release.
"We believe that these people should be released as soon as possible," Andrei Kelin, Russia's envoy to the OSCE, was quoted as saying.
"As an OSCE member, Russia will take all possible steps in this case," he said.
The group - believed to be military observers from Germany, Denmark, Poland, Sweden and the Czech Republic - is being held, along with several Ukrainian army personnel, by forces in the city of Sloviansk.
An OSCE spokeswoman in Vienna said the organisation had had "no direct contact with the eight observers being held."
Pro-Russian leaders in Sloviansk confirmed the observers' bus had been stopped and said they were checking the identities of those on board.
The self-proclaimed mayor of Sloviansk, Vyacheslav Ponomaryov, said at least one passenger had been carrying maps showing separatist checkpoints in the area, which suggested "their involvement in espionage".
Last weekend, Mr Ponomaryov broadcast an appeal to President Putin asking for Russian troops to protect the city from "fascists" after three of his men died in a gunfight.
Meanwhile, the G7 praised Ukraine for acting with restraint in dealing with the "armed bands" that had occupied government buildings.
But the group, which includes the US, UK, Germany, Japan, France, Canada and Italy, condemned Russia's "increasingly concerning rhetoric and ongoing threatening military manoeuvres."
The G7 was committed to intensifying sanctions on Russia, ahead of Ukrainian presidential elections next month, a statement said.
The US and EU already have assets freezes and travel bans in place targeting a number of Russian individuals and firms accused of playing a part in the annexation of Crimea.
In other developments:
- Ukraine's Prime Minister, Arseny Yatseniuk, has cut short a visit to Italy "because of the situation in the country"
- The US and the Ukrainian government accused Russian jets of violating Ukraine's airspace - a charge Moscow denied
- Crimea's Prime Minister, Sergei Aksenov, said there were back-up plans to guarantee the peninsula's water supplies although there was no problem with drinking water at present.