Police in Bangladesh have arrested a senior opposition politician, Salahuddin Quader Chowdhury, in the capital Dhaka.
A police spokesman said Mr Chowdhury was arrested on charges of instigating violence during an opposition-sponsored general strike in June.
But the government has also asked for his arrest on war crimes charges relating to the fight for independence.
Mr Chowdhury denies any wrongdoing during the 1971 war.
The BBC's Anbarasan Ethirajan in Dhaka says that it is the first time that a senior opposition Bangladesh Nationalist Party (BNP) official has been formally named as a war crimes suspect.
Mr Chowdhury was arrested at his home in Dhaka in connection with a murder case in June, deputy commissioner of police Monirul Islam told the AFP news agency.
"He has not been arrested in connection with any war crimes related cases," Mr Islam said.
Correspondents say that it is routine in Bangladesh for police to arrest suspects on one charge and then add multiple cases against them while they are in custody.
In July, leaders of the Islamic Jamaat-e-Islami party were arrested for "offending public religious sentiment" and then later charged with war crimes.
The war crimes tribunal on Wednesday said it had concrete evidence that Mr Chowdhury committed genocide, rape, arson and looting during the war of independence from Pakistan and charges on these cases were likely to follow.
The tribunal was established in March to try people suspected of atrocities during the independence campaign.
Prime Minister Sheikh Hasina's father, Sheikh Mujibur Rahman, played a prominent role in the campaign as did Zia-ur-Rahman, the husband of BNP leader Khaleda Zia.
The BNP and Jamaat have dismissed the tribunal as a political show trial.