Islamabad, Pakistan (CNN) -- At least 11 people have been killed and dozens wounded in a suicide attack Monday on a court building in the Pakistani capital, authorities said.
Two militants threw hand grenades, fired guns and then blew themselves up at the district court building, said Sikander Hayat, inspector general of Islamabad police.
Another police official, Jamil Hashmi, said that there were other armed attackers who opened fire and then left the scene. Police are still in the process of establishing exactly what happened, he said.
Witnesses at the court building told CNN they saw two men firing indiscriminately at people.
Attacks of this nature are rare in Pakistan's heavily policed capital.
The Pakistan Institute of Medical Sciences, a complex that includes a hospital, reported the death toll of 11 and said 39 people were wounded in the attack. The dead included a judge, authorities said.
The court building is in an upmarket residential district in central Islamabad. The area around the courts includes supermarkets, restaurants and coffee shops.
A little-known organization calling itself Ahrar Ul Hind claimed it had carried out the attack. It targeted the courts because it considers them to be un-Islamic, said Asad Mansoor, a spokesman for the group.
In a statement last month, Ahrar Ul Hind said that it had had ties with the Pakistani Taliban, but that the relationship had broken down because of the Taliban's focus on Pakistan's tribal areas.
Ahrar Ul Hind claims it wants to impose Sharia, or Islamic law, in Pakistan, India and around the world. It says it aims to achieve its goal by carrying out attacks on cities.
The Pakistani Taliban, which on Saturday declared a month-long cease-fire, denied any involvement with the Islamabad attack Monday.
Shahidullah Shahid, a spokesman for the extremist group, said that the cease-fire was still in effect and that action would be taken against any faction that tried to break it.
Asked last month about Ahrar Ul Hind, Shahid claimed the Taliban knew nothing about the organization.
CNN's Sophia Saifi and Saima Mohsin reported from Islamabad, and CNN's Jethro Mullen wrote from Hong Kong. Journalists Adeel Raja, Saleem Mehsud and Zahir Shah Sherazi contributed to this report.