Nine people accused of fomenting an Iranian-backed coup have been arrested by the Azerbaijani authorities. This development occurs in a context of deterioration of relations between Baku and Tehran.

Azerbaijan arrested at least nine of its nationals, suspected of being linked to Iranian secret services and of plotting a coup and assassinations, officials said on Tuesday.

The latest round in tensions between Baku and Tehran, whose relations have traditionally been strained, came after the expulsion of diplomats from both countries.

On Tuesday, Azerbaijan’s law enforcement forces arrested people who “were working for Iranian secret services”, the interior ministry, security service and the office of prosecutor general said in a joint statement.

The statement gave nine names and said several other people had been arrested.

The group was plotting a “violent overthrow of the government and the assassinations of prominent personalities and senior officials”, the statement said.

The wave of arrests follows the detention of six Azerbaijani nationals in a different case in April. They were accused of being “recruited by Iranian secret services to destabilise the situation in the country”.

Azerbaijan is a close ally of Iran’s historical rival, Turkey.

Tehran also fears that Israel — a major weapons supplier to Azerbaijan — could use Azerbaijani territory for an offensive against Iran.

Ties between neighbours Azerbaijan and Iran further soured in January when a gunman stormed into Baku’s embassy in Tehran.

He killed a diplomat and wounded two embassy security guards.

The Azerbaijani foreign ministry blamed Iran for the shooting, a claim that the Iranian foreign ministry has rejected.

Earlier in May, Iran expelled four Azerbaijani diplomats. The foreign ministry said the move was “in response” to Baku’s expulsion of Iranian embassy staff in April.

Malo Pinatel, with AFP