Azerbaijan has arrested a former aide to President Ilham Aliyev and the head of a major company on coup charges, weeks before parliamentary polls.
Security has been tightened as the polling date approaches
The men are accused of planning a coup with opposition leader Rasul Guliyev.
Mr Guliyev, who had been living in the US, says he was stopped last week from returning to Azerbaijan to contest the election - a charge Baku has denied.
More than 20 Azeri officials have been arrested or sacked in recent weeks on suspicion of supporting Mr Guliyev.
The government has strengthened its position by acting against people it accuses of having links to the opposition, BBC correspondent Natalia Antelava says.
It has also sent a clear warning to those who might have considered switching sides before the election, Azerbaijan's first since Mr Aliyev took over the presidency from his father in 2003.
Akif Muradverdiyev, a former presidential chief of staff, and Fikret Sadigov, the head of chemical giant Azerkimya, were arrested for plotting a coup, Azeri officials said.
Mr Guliyev was held by Ukrainian officials in Simferopol
They join at least a dozen other Azeri officials arrested over the last few weeks, including a former finance minister, a former Baku police chief and a former health minister.
All are accused of involvement in Mr Guliyev's alleged plan to overthrow the government.
Mr Guliyev is a former ally of Azerbaijan's Soviet-era strongman, the late President Heidar Aliyev.
He moved to the US in the mid-1990s after being accused of embezzlement, a charge he denies.
His announcement that he planned to contest parliamentary elections in early November prompted a fresh warning from the Azeri authorities that he will be arrested if he attempts a return.
Mr Guliyev said last week that his aircraft was prevented from landing at Baku airport. The Azeris say he had abandoned plans to return.
When the plane stopped to refuel in Ukraine, Mr Guliyev was briefly arrested, continuing to London after his release.
In a conference call with supporters on Tuesday, he said: "The authorities won't be able to prevent my return."
President Aliyev has meanwhile eased restrictions on foreign observers monitoring the elections, Reuters news agency quotes state television as saying.
Non-governmental organisations that are largely funded from abroad will now be able to send their workers to observe the vote.
The president has reportedly also ordered indelible ink to be used to mark voters' fingers, reducing the risk of voting irregularities.
Washington recently expressed alarm that the November polls would not be fair.