Bangladesh police have charged Tareque Rahman, elder son of former prime minister Begum Khaleda Zia, of masterminding a grenade attack on an opposition political rally that killed 23 people, police and a lawyer said on Monday.

Prime Minister Sheikh Hasina, then the main opposition leader, was addressing the rally in Dhaka in August 2004 when the explosion occurred, wounding more than 150 people. Hasina suffered partial loss of suffering.

Police filed the charges late on Sunday in a Dhaka court, accusing Tareque and several others of plotting the attack, the country's worst case of political violence.

"Investigations conducted in this case showed Tareque Rahman was one of the masterminds of the attack," attorney Abu Abdullah said.

Tareque, political heir apparent to his mother, who was arrested in 2007 for alleged corruption, is now in London on medical parole.

If convicted, he faces the maximum penalty of life imprisonment.

Among the others charged for the attack are two ex-ministers and three former police chiefs.

Police initially charged militants from the outlawed Islamist group Harkat-ul Jihad and a few accomplices from Khaleda's Bangladesh Nationalist Party for trying to kill Hasina and the top leadership of her Awami League.

The BNP said the charges against Khaleda's son were politically motivated and intended to malign the opposition leader and her family.

Last month a Dhaka court sentenced Khaleda's younger son Arafat Rahman Koko to six years in jail for laundering millions of dollars taken as bribes from two foreign companies.

Koko is also away in Thailand on parole for medical treatment.

Reuters