The EU's foreign policy chief warned on Wednesday the bloc should brace for worsening relations with Russia after tensions soared with the Kremlin over Ukraine and jailed critic Alexei Navalny.

"We cannot discard that this negative trend continues and that we reach even more dangerous levels of deterioration," Josep Borrell told the European Parliament.

"We don't want to feed a dynamic of escalation, let it be clear. But we nevertheless are showing that we will not accept intimidatory tactics and that we have to respond to them if they happen."

Borrell's comments come after a spike in Western criticism against Moscow massing troops on the border with Ukraine, the deteriorating health of Navalny and a diplomatic row with the Czech Republic.

Borrell — who saw offers to cooperate rebuffed during a chastening trip to Moscow in February — said the overall trajectory of ties with the Kremlin was heading downhill.

"I see a worrying trend from Russian authorities that seems to be choosing to deliberately deepen the confrontation with the West, with us," he told lawmakers.

"We must therefore define a modus vivendi that will avoid permanent confrontation with a neighbour who seems to have decided to act as an adversary.

"I think that we have to be prepared for a long, hard period in our relationship with Russia," he warned.

Tensions have appeared to ease slightly on two fronts after Russia said it was drawing down forces deployed near the Ukrainian frontier for drills and transferred Navalny to hospital.

But a spat sparked by Prague's accusation that Russian intelligence was behind a deadly 2014 blast on Czech territory rumbled on Wednesday with Moscow kicking out seven diplomats from EU member states.

That move followed the coordinated turfing out of Russian embassy staff by some European capitals after tit-for-tat expulsions between Prague and Moscow.