Russian President Vladimir Putin insisted on Saturday that the incident in the Kerch Strait was a provocation during his working breakfast with German Chancellor Angela Merkel on the sidelines of the G20 summit in Buenos Aires in Argentina.

According to the Kremlin, Putin and Merkel had a detailed discussion on various topics. He gave a comprehensive explanation of last week's dispute in the Kerch Strait and emphasized that it was staged in the run-up to the election in Ukraine.

Three Ukrainian naval ships attempted to force passage through the Kerch Strait in Crimea, between the Black Sea and the Sea of Azov, last Sunday, before they were intercepted and captured by the Russian Coast Guard.

Crimea was incorporated into Russia in March 2014 following a local referendum. Ukraine said the peninsula was annexed.

Moscow has condemned Ukraine for violating Russian territorial waters but Kiev has declared a state of emergency over the incident, saying a "Russian invasion" was impending.

"All escalations must be avoided," Merkel told reporters after her meeting with Putin. "The freedom of shipping traffic in the Sea of Azov… must be ensured."

Merkel called on Russia to honor a 2003 treaty that sets out the conditions under which Ukrainian ships may enter the Sea of Azov and reach Ukrainian cities.

"Russia must stick to this," she said.

Discussions to continue

Merkel said Germany had suggested－and Russia agreed－that discussions about the dispute should continue at the adviser level in the four-way Normandy format that has sought to ease tensions between Ukraine and Russia.

Ukraine President Petro Poroshenko kept up the pressure from Kiev, saying Putin had refused to take his calls since the crisis flared up.

He said that when the incident happened, he instructed his office to set up a call with the Kremlin leader to say "we are ready for this negotiation to de-escalate … and unfortunately, until now, Putin did not answer my request for a direct phone conversation."

Poroshenko told France 24 in an interview that Ukraine would try to resolve the standoff diplomatically but insisted Russian forces withdraw from Crimea, and return its ships and sailors "captured illegally in the neutral waters of the Black Sea".

Meanwhile, Putin replied that there would be no end to the conflict with Ukraine "as long as the current authorities remain in power".

"The current Ukrainian authorities have no interest in resolving the conflict, especially by peaceful means," the Agence France-Presse quoted Putin as saying at the summit.

"As long as they remain in power, the war will continue," the Russian leader added.

Putin also said he briefed his US counterpart Donald Trump on the Ukraine crisis.

Putin said he explained Moscow's position to the US president when the leaders met briefly at a summit dinner on Friday, AFP reported.

"We spoke standing up. I replied to his questions about the incident in the Black Sea," Putin said.

Meanwhile, the Kremlin hopes that Trump and Putin can meet and hold talks before a G20 summit in Japan in June next year, a Kremlin aide said on Saturday, according to a report by Reuters.