A massive Russian aid convoy rumbled towards Ukraine's border on Wednesday as Kiev vowed to block what it feared could be a "Trojan horse" bringing military assistance to pro-Kremlin rebels fighting a bloody insurgency in the east.

Russian television images showed a line of nearly 300 lorries moving through the countryside, covered with white tarpaulin and stretching over almost three kilometers (two miles).

Western sanctions against Russia will not affect the country's multi-billion dollar weapons sales, the state-owned arms export company said Wednesday.

German Chancellor Angela Merkel warned Wednesday against severing ties with Russian President Vladimir Putin over the Ukraine crisis but said he must also do his part.

Merkel told the Saechsische Zeitung newspaper she was "working very hard to keep the lines of communication open" with Putin despite the EU's decision last month to level sanctions against Russia over its actions in the ex-Soviet state.

Japan will lodge a "strong protest" with Russia over  military exercises reportedly being held on the disputed Kuril islands, Prime Minister Shinzo Abe said Wednesday. 

"I can't accept this at all," he told reporters in response to questions about the drills.

Moscow police on Tuesday detained dozens of protesters who had gathered outside the Ukrainian embassy to show their support for Kiev in its campaign against pro-Russian insurgents in the separatist east.

The private Moscow Echo radio station said about 200 people gathered for the demonstration before being dispersed by the police.

Russian President Vladimir Putin on Tuesday hosted his Egyptian counterpart Abdel Fattah al-Sisi for talks about Cairo's purchase of advanced surface-to-air missiles and membership in a Moscow-led free trade zone.

The two strong-willed leaders have developed a close working relationship since Putin gave his backing to Sisi's presidential run during the latter's visit to Moscow in February.

Russia will not pay for the Mistral warships being built by France until both ships have been delivered, an official said on Tuesday.

A convoy of 262 Russian trucks rolled toward the Ukrainian border on Tuesday as Kiev vowed to block the aid mission from its territory over fears it was a ploy to bolster pro-Kremlin rebels.

The convoy of what Russia says is humanitarian aid has sparked fears of an escalation in a conflict that has left hundreds dead in eastern Ukraine in recent months and plunged Moscow's ties with the West to their lowest point in decades.

European Commission head Jose Manuel Barroso warned Russian President Vladimir Putin in a phone call Monday against any unilateral intervention in Ukraine, including for humanitarian reasons.

"Speaking with President Putin, President Barroso said that the EU would join in international efforts to assist people in need as a result of the conflict," a commission statement said.

The Kremlin said Monday that Russia was sending a "humanitarian convoy" to eastern Ukraine despite Western fears that the mission might be used as a cover for intervention.

"The Russian side is sending a humanitarian convoy to Ukraine in cooperation with representatives of the International Committee of the Red Cross," President Vladimir Putin told European Commission head Jose Manuel Barroso on the phone, according to a Kremlin statement.