Gunmen attacked a police station early Thursday in the Sinai town of el-Arish, Egyptian officials said. No injuries were reported in the attack but clashes continued throughout the early morning hours, security sources told Palestinian (Ma'an) news agency as the army continued its second day of operations against extremist elements in the Sinai. "A large army force backed by armored (forces) raided the al-Toma village, one of the Sheikh Zuwaid villages, which is considered the stronghold of terrorist elements since the Sinai bombings in 2005," a military source explained. The attack on al-Toma used an Apache helicopter and did not pass unnoticed by a peacekeepers' camp in the area. Several peacekeeping troops witnessed missile fire from the helicopter. The leader of a Salafi group in the Sinai denied involvement in the police station attack. "We are carefully observing the ongoing security campaign in the Sinai. Despite the terrorist attacks on the police station, tribes did not carry out violent acts," Sheikh Abdullah al-Jahamah, the head of the al-Mujahidin association, told Ma'an. A day earlier the Egyptian army launched airstrikes in the Sinai Peninsula targeting extremist groups and killing over 20 militants in a response to an attack that killed more than a dozen soldiers on Sunday.