Australia has joined the international response to Russia's apparent nerve agent attack on a former double agent on British soil.  The government announced that two Russian diplomats would be expelled.

The government declared the pair to be undeclared intelligence officers and gave them a week to leave.

"The brazen attack, the criminal attack in the United Kingdom, in Salisbury on the 4 March, was an attack on all of us," said Prime Minister Malcolm Turnbull.  "It was an attack on the sovereignty of every nation that respects the rule of law and that is why we are taking this action today."

In a diplomatic coup for London, more than twenty nations are taking part by expelling more than 100 Russian diplomats and security officials.  The UK led the pack by giving 23 Russian officials their notice to vacate the country, while working behind the scenes to secure commitments from US, Australia, the EU and a couple of neighboring European nations. 

The US overnight announced it was expelling 60 Russians; Mr. Turnbull and Foreign Minister Julie Bishop announced Australia's contribution at a joint news conference on Tuesday. 

Ms. Bishop said, "We share the outrage of the British government and other allies and partners over the deployment of a military grade nerve agent, in an attempted assassination in Salisbury, in the United Kingdom."

The UK says The Kremlin was responsible for the nerve agent attack in Salisbury on 4 March, the first chemical attack on European soil since the end of World War II.  The targets, former double agent Sergei Skripal and his daughter Yulia, remain hospitalized in a critical condition.  Russia denied any involvement.