Nabeel Rajab's illness comes after government speeds up court proceedings to dissolve leading opposition party
Bahrain's leading human rights activist was transferred back to jail on Wednesday despite being in ill health, as the authorities launched another round of arrests.
Nabeel Rajab was returned to jail after he was discharged from the Bahrain Defence Force hospital on Wednesday.
Rajab had been rushed to the coronary care unit on Tuesday with an irregular heartbeat.
"Nabeel never suffered heart problems before," said Sumaya Rajab, Nabeel's wife, in a statement. "My husband is a human rights defender and does not deserve this treatment."
Rajab's family stated he had lost 7kg since his arrest and developed high blood pressure.
"His heart beats are irregular. His skin has yellowed in colour," said a statement released to the Bahrain Institute for Rights and Democracy (BIRD).
"The toilets are filthy, to the extent that he eats less to avoid needing them, and the showers have extremely low pressure."
His worsening condition comes as the government made more arrests of alleged Shia militants in the country.
On Wednesday a court jailed six Bahrainis for life and two for 15 years after convicting them of "spying" for Iran, a judicial source said.
The criminal court also stripped all eight of their citizenship, the source added.
The court also found them guilty of "joining a terrorist group, possessing arms, ammunition and explosives," and training in their use, the source said.
Opposition bloc lawyers withdraw
Defence lawyers for Bahrain's main Shia opposition bloc Al-Wefaq withdrew on Tuesday from court proceedings to dissolve it in protest at the government's push to accelerate the process.
The administrative court had already suspended all of the party's activities on 14 June, ordering its offices closed and assets frozen in a move that drew concern from the UN and the US.
The bloc was the largest in parliament before its MPs resigned in protest at the crushing of 2011 protests calling for an elected government.
The lawyers said authorities had also refused to allow them access to documents at the bloc's headquarters.
"Therefore, the defence team has withdrawn from the case," they said in the statement.
Initially, the court had not been scheduled to meet on the government's request to dissolve Al-Wefaq until 6 October but brought the session forward to last Thursday at the request of Justice Minister Sheikh Khaled bin Ali Al-Khalifa.
A new session was held on Tuesday instead of 4 September as previously agreed, and the next hearing was set for Monday.
The justice ministry has accused the bloc of providing a haven for "terrorism, radicalisation and violence" and opening the way for "foreign interference" in the kingdom's affairs.
That was an allusion to Iran, which Sunni-ruled Bahrain accuses of fomenting unrest among its Shia majority.
Tiny but strategic Bahrain lies just across the Gulf from Iran and is the home base of the US Fifth Fleet.
Earlier this month, leading Iranian general Qassem Suleimani warned Bahrain that its decision to strip the Gulf state's Shia spiritual leader Sheikh Isa Qassim of his citizenship would fan "armed rebellion" in the kingdom.
Last month, an appeals court more than doubled a four-year prison sentence handed down against Al-Wefaq leader Ali Salman on charges of inciting violence.