AMMAN, Oct 11 (Reuters) - A large bomb exploded in an area housing security and army compounds west of Umayyad Square in central Damascus on Thursday, opposition activists said.

Islamist groups Ahfad al-Rasoul and Ansar al-Islam said in a joint statement they planted bombs in a compound belonging to State Security in the area.

Syrian state television said a "terrorist explosion" had injured two people. Witnesses said soldiers in full combat gear were deployed in the area and all roads leading to Umayyad Square were cut.

Ansar al-Islam claimed responsibility for a bomb attack last month on the army's Chief of Staff headquarters in Umayyad Square, which started a large fire in the building.

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  • Standing in front of a row of plastic tents a young boy flashes the V-sign in a refugee camp on the border between Syria and Turkey near the northern city of Azaz on December 5, 2012. The internally displaced faced further misery as heavy rain was followed by a drop in temperatures. The United Nations estimated late October that more than 2.5 million people have been affected by the fighting in Syria. There are more than 348,000 Syrian refugees registered in neighbouring countries, but many more are unregistered. Credit: ODD ANDERSEN/AFP/Getty Images

  • Syrian refugees react as United Nations Secretary General Ban Ki-Moon (unseen) arrives for a visit in the Zaatari Refugee Camp, on December 7, 2012. UN chief Ban Ki-moon appealed Friday for more aid to help hundreds of thousands who have fled the Syrian conflict, as he visited a refugee camp in neighbouring Jordan.(KHALIL MAZRAAWI/AFP/Getty Images)

  • A Syrian boy, who fled his home with his family due to fighting between government forces and rebels, stands near his tent at a refugee camp near the Turkish border, Azaz, Syria, Sunday, Oct. 7, 2012. (AP Photo/ Manu Brabo)

  • An elderly Syrian woman, who fled her home with her family due to fighting between government forces and rebels, chants, "Allah," meaning God in Arabic, inside her tent at a refugee camp near the Turkish border, in Azaz, Syria, Sunday, Oct. 7, 2012. (AP Photo/ Manu Brabo)

  • A Syrian woman, who fled her home with her family due to fighting between government forces and rebels, stands near her tent at a refugee camp near the Turkish border, Azaz, Syria, Sunday, Oct. 7, 2012. (AP Photo/ Manu Brabo)

  • A Syrian man, who fled his home with his family due to fighting between government forces and rebels, plays with his nephew near their tent at a refugee camp near the Turkish border, Azaz, Syria, Sunday, Oct. 7, 2012. (AP Photo/ Manu Brabo)

  • Syrian women, who fled their homes due to fighting between government forces and rebels, drink tea inside their tent at a refugee camp near the Turkish border, Azaz, Syria, Sunday, Oct. 7, 2012. (AP Photo/ Manu Brabo)

  • Syrians, who fled their homes with her families due to fighting between government forces and rebels, sit in their tent at a refugee camp near the Turkish border, Azaz, Syria, Sunday, Oct. 7, 2012. (AP Photo/ Manu Brabo)

  • Syrias, who fled their homes with their families due to fighting between government forces and rebels, take refuge at a camp near the Turkish border, Azaz, Syria, Sunday, Oct. 7, 2012. (AP Photo/ Manu Brabo)

  • A Syrian woman, who fled her home with her family due to fighting between government forces and rebels, sits near her tent at a refugee camp near the Turkish border, in Azaz, Syria, Sunday, Oct. 7, 2012. (AP Photo/ Manu Brabo)

  • A Syrian girl, who fled her home with her family due to fighting between government forces and rebels, flashes the victory sign at a refugee camp near the Turkish border, Azaz, Syria, Sunday, Oct. 7, 2012. (AP Photo/ Manu Brabo)

  • A Syrian boy, who fled his home with his family due to fighting between government forces and rebels, plays near his tent at a refugee camp near the Turkish border, Azaz, Syria, Sunday, Oct. 7, 2012. (AP Photo/ Manu Brabo)

  • Syrians, who fled their homes with their families due to fighting between government forces and rebels, wait for food distribution from an NGO at a refugee camp near the Turkish border, in Azaz, Syria, Sunday, Oct. 7, 2012. (AP Photo/ Manu Brabo)

  • A Syrian boy, who fled his home with his family due to fighting between government forces and rebels, holds a plate with food to eat at a refugee camp near the Turkish border, Azaz, Syria, Sunday, Oct. 7, 2012. (AP Photo/ Manu Brabo)