The leaders of Germany and France, carrying a peace plan that reportedly incorporates proposals from Russia, have met Ukraine President Petro Poroshenko in an effort to bring an end to fighting in eastern Ukraine.

Thursday's trip to Kiev by German Chancellor Angela Merkel and French President Francois Hollande will be followed by a meeting with Russian President Vladimir Putin in Moscow "based on the territorial integrity of Ukraine".

The meeting with Poroshenko ended late on Thursday and Hollande and Merkel left the presidential offices without comment. Details of their plan remained unclear, although Poroshenko said that it raised hopes for calling a quick ceasefire.

Russia vehemently denies that it is providing equipment or troops for the pro-Russian fighters in eastern Ukraine, but John Kerry, US secretary of state, sharply rejected that denial on Thursday.

"Let there be no doubt about who is blocking the prospects for peace here," Kerry said in Kiev, where he met Poroshenko just hours before Merkel and Hollande did.

Shuttle diplomacy

Pavlo Klimkin, Ukraine's foreign minister, said on Twitter that the two European leaders and Poroshenko discussed "steps so that the Minsk agreement can start working".

That refers to a pact reached in September that called for a ceasefire, the withdrawal of heavy weaponry by both sides, international monitoring of the Ukraine-Russia border and a degree of autonomy for the east.

The shuttle diplomacy comes as concerns rise about whether the US will grant lethal aid to Ukraine and as NATO forms a quick-reaction force of 5,000 soldiers in response to the security crisis.

Inside Story: Is US risking another proxy war with Russia?

The fighting in eastern Ukraine between pro-Russian fighters and government forces has intensified sharply over the past two weeks.

Germany and other European nations remain fiercely opposed to sending arms to Ukraine.

Federica Mogherini, EU's foreign policy chief, backed the French-German peace effort, saying "there is no military solution to the crisis in Ukraine".

In a sign of the importance of the initiative, this will be Merkel's first trip to Moscow since Ukraine's conflict broke out last year.

"It will not be said that France and Germany together have not tried everything, undertaken everything, to preserve the peace," Hollande said earlier.

The resurgent unrest has killed eight more people in eastern Ukraine and prompted fears the conflict is threatening Europe's overall security.

At least three people were killed in overnight shelling in the rebel stronghold of Donetsk, local officials said on Thursday, and Ukraine said five soldiers were killed and 29 others wounded in the last 24 hours.

More than 5,300 people have been killed since the fighting started in April.

Russian response

In Moscow, a Putin adviser welcomed the new European initiative and said the Kremlin was ready for a constructive discussion.

Yuri Ushakov said Russia was "ready for a constructive conversation" aimed at stabilising the situation, establishing a dialogue between the Ukrainian government and the rebels, and rebuilding economic ties between eastern Ukraine and Kiev.

Nevertheless, Kerry urged Russia to show its commitment to a peaceful, diplomatic solution to the conflict in eastern Ukraine by ceasing its military support for the separatists and bringing them to the negotiation table.

Fighting rages in eastern Ukraine despite diplomacy

"Our choice is diplomacy," Kerry said after his talks with Poroshenko on Thursday, making no mention of providing lethal military aid to Ukraine.

At a later joint news conference with Arseniy Yatsenyuk, Ukraine's prime minister, Kerry, who brought $16.4m in new humanitarian aid, said President Barack Obama "is reviewing all his options; among those options obviously is the possibility of providing defensive systems to Ukraine".

"We are not interested in a proxy war. Our objective is to change Russia's behaviour," he said.

US air force General Philip Breedlove, the top NATO commander, has said that Russia continues to supply the Ukrainian separatists with heavy, state-of-the-art weapons, air defences and fighters.

For their part, NATO defence ministers in Brussels on Thursday boosted the alliance's emergency forces because of the fighting in Ukraine among other security challenges.

Jens Stoltenberg, NATO secretary-general, said the alliance boosted the size of the Response Force from 13,000 to 30,000. NATO also moved to form a quick-reaction force of 5,000 ground troops.

Source: Al Jazeera And Agencies