(Updates death toll, adds details, background)
CAIRO, March 15 (Reuters) - Unidentified gunmen opened fire on an army police checkpoint on the outskirts of Cairo on Saturday, killing six officers, Egyptian state TV reported.
A senior security source told state TV that two bombs found near the checkpoint had also been deactivated. The army blamed the attack on ousted Islamist President Mohamed Mursi's Muslim Brotherhood group, according to a military statement.
The Brotherhood was not immediately available to comment.
There have been several militant attacks on security forces since the army overthrew Mursi last July and about 300 security officers have been killed.
Analysts expect attacks on security forces to increase in the coming months when a presidential vote is due to take place and is expected to be won by army Field Marshal chief Abdel Fattah al-Sisi.
One army officer was killed in an attack on an army bus on Thursday which Egypt also blamed on the Brotherhood, declared a terrorist group by the government in December.
The Brotherhood, which says it is committed to peaceful activism, condemned Thursday's attack and accused the military-backed government of trying to implicate it for political reasons.
Sinai-based militant group Ansar Bayt al-Maqdis has claimed responsibility for a series of high-profile attacks on senior security officials, including an assassination attempt on the interior minister last year.
(Reporting by Ali Abdelaty; Writing by Yasmine Saleh; Editing by Pravin Char)