NATO Secretary General, Anders Fogh Rasmussen has condemned the alarming build up of Russian ground and air forces near the border with Ukraine, where pro-Russian separatist groups are fighting the Ukrainian military.

Rasmussen said in a statement: "We have also seen transfers of large quantities of advanced weapons, including tanks, armoured personnel carriers and artillery to separatist groups in eastern Ukraine."

Over 100 trucks from a Russian aid convoy entered into the country on Friday (22 August), without permission, and have now been seen arriving in the eastern city of Luhansk, where pro-Russian separatists are fighting the Ukrainian forces.

The trucks are reportedly carrying water, generators and sleeping bags to help civilians in Luhansk, reported Sky News. "We consider this a direct invasion by Russia of Ukraine. Under the cynical guise of the Red Cross these are military vehicles," said Ukraine's State Security Chief, Valentyn Nalivaychenko in a statement to journalists.

Previously it was agreed that the Russian trucks can enter into eastern Ukraine, if accompanied by the International Red Cross, however, the international charity pulled out after not receiving sufficient security guarantees.

Ukrainian President Petro Poroshenko has said that the convoy entering into Ukraine is a "flagrant violation of international law". While, United States has called on Russia to pull out its convoy immediately from Ukraine or risk facing more sanctions, reported Reuters.

Despite suspicions by Kiev that the trucks are carrying supplies for pro-Russia separatist fighters, Russian President Vladimir Putin has warned against the blocking of the convoy, reaffirming that it is purely humanitarian.