"The imposition of martial law in several regions could potentially lead to the threat of an escalation of tension in the region of the conflict, in the southeast (of Ukraine)," he said.
Kiev imposed martial law Monday for 30 days in parts of the country after the President of Ukraine Petro Poroshenko argued that there is an "extremely serious" threat of an invasion of the territory by Russia.
President Vladimir Putin spoke to Angela Merkel on phone Tuesday saying that Ukraine is to blame for the newest conflict and confrontation in Crimea. According to him, Ukraine provoked confrontations for political reasons.
On Sunday, three ships belonging to the Ukrainian Navy was captured by Russia for illegally crossing into its territorial water in the Black Sea.
When asked whether Russian President Vladimir Putin will discuss the issue with the United States President Donald Trump, Peskov said, according to Russian state media TASS, “This is not a topic for the G20 summit, but at the same time if any issues are raised at bilateral meetings with the president on the sidelines of the summit, no one should doubt that the president will give exhaustive clarifications.”
The Ukrainian sailors captured by Russia confessed that they ignored Russian orders to stop and continued according to a footage released by Russian state media.
On Nov. 25-26 two attacks were carried out on Russian diplomats in Kiev and Kharkov respectively leading to two criminal cases by the Russian Investigative Committee.
"The main directorate of the Russian Investigative Committee has initiated two criminal cases on the basis of the offense under Article 360 Part 2 of the Russian Criminal Code ("Attacks on persons or buildings under international protection")," said the Committee Spokesperson Svetlana Petrenko.
On the other hand, Ukraine wants Western countries to impose new sanctions on Moscow. Several senior European politicians Tuesday raised the possibility of new sanctions against Russia.
Karin Kneissl, foreign minister of Austria, which holds the European Union’s rotating presidency, said the EU would consider sanctions depending "on the exposition of facts and the further conduct of both parties".
Poland and Estonia expressed support for more sanctions.
Senior German conservative Norbert Roettgen, a close Merkel ally, said the European Union may need to toughen its sanctions against Russia, imposed partly on Moscow over the Crimea conflict.
A court in Crimea ordered the first of 24 Ukrainian Navy sailors captured by Russia to be detained for two months, the TASS news agency reported on Tuesday.
Since 2014, the Black Sea region has been a cause of conflict between Russia and Ukraine over Crimea due to the Russian annexation of Crimea following the result of a popular referendum in the peninsula according to which 96.6 percent of the citizens voted to be separate from Ukraine.