Russia has said it reserves the right to respond to Sweden's expulsion of two Russian diplomats over alleged espionage at telecoms and defence giant Ericsson.

The Swedish decision gave rise to "surprise and regret", the Russian Foreign Ministry said, adding that it "reserves the right to make the appropriate response to such an action" - thought to mean tit-for-tat expulsions.

The Russian side reserves the right to make an adequate response to the latest step

Russian Foreign Ministry

Two Russian diplomats were declared persona non grata and have left Sweden over spying allegations, Swedish officials confirmed on Monday.

They have been expelled in connection with the Ericsson case as "their activities were not compatible with their diplomatic status", Swedish Foreign Ministry spokeswoman Maria Hakansson told BBC News Online.

Although best known for its mobile and office phones, Ericsson is a major manufacturer of radar and missile-guidance technology for the Gripen fighter jet, Sweden's main strike warplane.

About 2,000 of Ericsson's 72,000 employees work in the group's defence operations, primarily in the subsidiary Ericsson Microwave Systems.

Secrecy breach

Five Ericsson staff are now under investigation for passing secrets to a foreign power.

Ericsson makes more than just mobiles

Ericsson suspended two workers on Friday, after three current and former employees were taken into custody earlier in the week.

The three are being held on suspicion of passing secret documents to an unnamed foreign intelligence service.

According to court documents, their detention is the result of a month-long police surveillance operation.

No formal charges have been filed against the three men.

Another two have been suspended at the company on suspicion of breaking Ericsson's security rules.

Ericsson has said none of the five people involved held high positions in the company and it did not believe the information leaked would cause any major damage to the company.

Defence matter

The Swedish media has speculated that the documents could concern radio equipment or radar systems, such as those manufactured by Ericsson for the Anglo-Swedish JAS-39 Gripen jet.

Leading daily Dagens Nyheter suggested on Friday that the Russian espionage could be a tit-for-tat response to Sweden's purchase in recent years of top secret information on Russia's air radar system.

The Russian information would have been used to help to test and develop the efficiency of the JAS radar system, the paper said.

Saab Aerospace, a joint venture of Sweden's Saab AB and Britain's BAE Systems Plc that makes the Gripen fighter, said the company was not affected by the affair.