By Michael Georgy
CAIRO (Reuters) - Egyptian security officials said on Tuesday that authorities had arrested a supporter of deposed Islamist President Mohamed Mursi suspected of involvement in a rocket-propelled grenade attack on a state-owned satellite station in Cairo.
Any link between the suspect and Mursi in the October 7 attack in the capital is likely to be used to justify tougher measures against Islamists, who authorities have portrayed as terrorists since the army seized power on July 3.
Two people were wounded in the attack in the Maadi suburb of Cairo, the same day that suspected militants killed six Egyptian soldiers near the Suez Canal.
Security officials said a clothes merchant identified as Moataz Mahmoud had been detained. Authorities found weapons including parts of an RPG resembling the ones used in the Maadi attack and a machinegun in his apartment, they said.
"We have strong suspicions that he was involved in the attack," said one of the security officials, adding that the man is a supporter of Mursi.
Security officials said Mahmoud participated in a weeks-long sit-in in northeast Cairo that was organized by Mursi's Muslim Brotherhood movement.
Police and soldiers moved in to clear the vigil in August, killing hundreds of protesters. Brotherhood supporters said Egyptian forces shot at unarmed civilians, but the authorities said they were defending themselves after coming under attack.
Authorities accused the Brotherhood of storing weapons at the site, an allegation the movement has denied.
Egypt has been thrown into political turmoil since the army toppled Mursi and installed an interim government after mass protests against his rule.
The turmoil has hammered tourism and investment in a country at the heart of the Middle East. Western allies are keeping a close eye on Egypt, which has a peace treaty with Israel and controls the Suez Canal, a vital global trade route.
Authorities make no distinction between the Brotherhood, which is now outlawed in Egypt, and al Qaeda-inspired militants in the Sinai Peninsula who have dramatically stepped up attacks on security forces since Mursi's ouster.
The Brotherhood says it is a peaceful group, and that the government makes allegations against it to justify a crackdown that has killed hundreds. More than 2,000 Brotherhood supporters have also been arrested, including Mursi and other top leaders.
Military and security officials say the Brotherhood's real intention was to establish a single Islamic nation across several countries, and that Egypt's national interests were not its priority - allegations it denies.
Fears are growing that an Islamist insurgency could take hold beyond the Sinai and across Egypt. A Sinai-based group claimed responsibility for a failed suicide bombing that targeted Egypt's interior minister in Cairo in September.
There have been several attacks on policemen in the capital.
In order to counter what it says is a rising threat from terrorism, Egypt has imposed a state of emergency and an overnight curfew.
(Editing by Mike Collett-White)