Both British and Russian officials seemed keen to play down the incidents, and a spokeswoman for the British embassy in Moscow even suggested that the expulsions had nothing to do with espionage.
She pointed out that neither the Russian diplomat expelled from London nor John Scarlett, the British diplomat expelled from Moscow, had been declared persona non grata, the term usually applied in spying cases.
However, Russian intelligence sources said privately that Mr Scarlett was the MI6 station chief in Moscow.
The decision not to use the persona non grata label, and the reluctance of both countries to exchange indignant rhetoric, point to a common desire to return as soon as possible to a normal working relationship. 'We hope this is an end to the affair,' a Foreign Office spokesman said. Although Russia demanded Mr Scarlett's withdrawal last month, word of his expulsion and the British response did not emerge until Thursday evening.
The news coincided with the appearance on Russian television of Vadim Sintsov, a defence official arrested in January on charges of spying for Britain under the codename Demetrius. The programme said Russian counterintelligence had arrested 20 agents in Russia last year
Mr Sintsov, a middle-aged man who was shown sitting behind a table in a bare room, alleged that British intelligence agents had recruited him to provide information on Russian arms sales to Middle Eastern countries. The British had also been interested in 'general questions of how we are organising weapons sales'. He added: 'A certain James Self began to work with me. And some time after that, he introduced me to his successor as liaison officer. They used to meet me on the territory of other countries outside Russia. At some point in the autumn, they started to work on the possibility of maintaining connections here.'
A television commentator suggested that MI6 had managed to recruit Mr Sintsov after gathering compromising information about him. He was said to have received dollars 12,000 ( pounds 8,000) in payment. He is charged with high treason, an offence which carries the death penalty.
Russian newspapers have frequently implied a link between the Sintsov affair and the arrest in February of Aldrich Ames, a senior CIA operative accused of spying for Moscow. The Russians did not disclose Mr Sintsov's arrest until after the Ames case had become public knowledge.
Western intelligence sources said the Russians were angry that Washington had made such a hullabaloo over the Ames affair. They said the Americans' handling of the case - depicted in Washington as one of the worst spying scandals in American history - had increased the Russians' determination to demonstrate that Western agents were still active on Russian soil.
'Foreign intelligence services do exist in Russia, and sometimes they lose a sense of proportion, the feeling of being guests. They start to act from the point of view of their interests, and quite openly.
Agents remain the main weapon of intelligence,' said Alexander Mikhailov, a spokesman for the Federal Counterintelligence Service, an offshoot of the former KGB.Reuse content