The 81-year-old head of Sudan’s main opposition coalition has been admitted to a police hospital after more than two weeks in detention.

The 81-year-old head of Sudan's main opposition coalition has been admitted to a police hospital after more than two weeks in detention, his daughter and lawyer said on Tuesday.

Farouk Abu Issa, head of the umbrella group National Consensus Forces, was detained on Dec. 7 for signing a unity deal with armed rebels.

"This is the first time we have seen him since he was arrested, and we are very worried about his health," his daughter Nahla Abu Issa told Reuters by phone. She said he suffers from high blood pressure, diabetes and heart problems.

Sudan, which is facing insurgencies in Darfur and two southern provinces, has warned that politicians who form links with the rebels will face consequences. Activists say security forces are cracking down ahead of an election in April, in which President Omar al-Bashir is expected to extend his 25 years in power.

The opposition and rebels insist on linking issues of political reconciliation with progress on ending the wars, a stance which contributed to the breakdown of ceasefire talks earlier this month.

Amin Mekki, a 75-year-old activist who was arrested with Abu Issa after they signed their largely symbolic unity agreement with the rebels, remains imprisoned. The Sudan Observatory for Human Rights, which Mekki used to head, was raided earlier this week by security services.

Abu Issa and Mekki were charged with undermining the constitution, stirring hatred against the state and encouraging the war against it, Abu Issa's lawyer Nabil Adib said.

The National Intelligence and Security Services, Sudan's state security agency which arrested the two leaders, could not be reached for comment.