Moscow said on Friday it would cap the number of the Czech embassy staff in a tit-for-tat move after the EU country announced it was expelling dozens of Russian diplomats.

The Czech embassy in Moscow will lose 91 local hires, the foreign ministry said, in a move that could hamstring the operations of the EU country's diplomatic mission.

"The Czech authorities' irresponsible and provocative behaviour delivered a painful blow to their own diplomatic service," a foreign ministry spokesperson said in a statement to AFP.

Prague said the move was an "important technical and administrative complication" in a statement issued by the foreign ministry.

Tensions have spiralled between the two countries after Prague accused Russian military intelligence of being behind a deadly explosion at an ammunition depot in eastern Czech Republic in 2014.

Prague has expelled 18 Russian embassy staff over the incident, with Moscow kicking out 20 Czech embassy staff in retaliation.

On Thursday, Prague said it would slap a ceiling on Russian diplomat numbers in line with the Vienna Convention on Diplomatic Relations, aiming at parity.

The Czech government said Russia would have until the end of May to withdraw another 63 embassy employees to reduce their numbers to the same level as those of the Czech embassy in Moscow.

The Russian foreign ministry spokesperson said that Moscow would also limit the Czech embassy workforce in the Russian capital, meaning that the embassies of the two countries would have seven diplomats each by May 31.

The two countries' diplomatic missions will also have 25 administrative employees and 19 local hires.

The cuts mean that the Russian embassy staff in Prague will lose 35 diplomats and 46 administrative employees, Moscow said.

By contrast, the Czech embassy in Moscow will lose 16 diplomats, four administrative staff and 91 local hires.

Prague said in the statement the local hires working at the embassy and the Czech House hotel did not perform diplomatic or consular activities.

"We will have to include the fact of this reduction in our talks on parity when it comes to the two embassies' workforce in the future," the foreign ministry said.