BERLIN, March 13 (Xinhua) -- German Chancellor Angela Merkel on Tuesday condemned in strongest terms the toxin attack in Salisbury in a phone call with her British counterpart Theresa May.

According to a statement from German government spokesperson Steffen Seibert, Merkel said she took the British government's assessment of the issue of Russian responsibility for the attack extremely seriously.

It is up to Russia to respond swiftly to legitimate questions from the British government and to call for full and prompt disclosure of the relevant chemical weapons program to the Organization for the Prohibition of Chemical Weapons (OVCW), said Merkel.

Merkel and May agreed to stay in close contact and to discuss together with the allies and European partners in an appropriate manner, the statement said.

The phone call between the two heads of governments came as a former Russia spy and his daughter in London on March 4 were targeted with a military-grade nerve agent of a type developed by Russia. The two remain in a critical condition in hospital.

May on Monday pointed her finger at Russia over a developing "poisoning attack" row, claiming that her government had concluded it was "highly likely" that Moscow was responsible for the attack.

On Tuesday, Russian Foreign Minister Sergei Lavrov said that Russia, while denying any involvement in the poisoning case, was ready to cooperate with Britain in the investigation of the incident in accordance with international law.

"Russia is innocent and Russia is ready to cooperate in accordance with the Chemical Weapons Convention if the United Kingdom condescends to honoring its international legal obligations related to the mentioned document," Lavrov told a press conference in Moscow.