US and EU governments ask for release of Kremlin critic Alexei Navalny

The US and several European governments have called for the immediate release of leading Kremlin critic Alexei Navalny after he was detained at a Moscow airport on Sunday.

The opposition figure, 44, was turning home from a convalescence in Germany five months after an effort on his life in a nerve agent poisoning he charges on Russian officials.

President Vladimir Putin's government has rejected responsibility for the attack.

On Monday morning, Navalny was staying held in a Moscow police cell and had yet to be given access to his lawyers.

The US and the EU led calls on Monday for Putin's fiercest critic to be released but have stopped short of advancing retaliatory action.

US Secretary of State Mike Pompeo said he was "deeply troubled" at the news of Navalny's arrest. In a thinly-veiled criticism of the Russian government, he added that "confident political leaders do not fear nor see the need to commit force against or wrongfully detain, political opponents."

"We also continue to require a total and independent investigation on the attack on Alexei Navalny's life," it went on.

Taking to Twitter, Charles Michel, the President of the European Council, issued a demand for Russian officials to release Navalny immediately, branding the move to keep him as "unacceptable."

Other EU countries have also added their voice to calls for the politician to be freed. France showed "great concern" at the news and urged for his immediate release.

"Together with its European partners, it is developing his situation with the utmost vigilance and calls for his immediate release," the French foreign ministry said in a statement.

German Foreign Minister Heiko Maas said Navalny's arrest is "incomprehensible" and that "he should be delivered immediately."

"Navalny was the victim of a serious poisoning attack on Russian soil. We continue to expect that Russia does everything possible to fully investigate this illness and to bring the perpetrators to justice," he added.