CAIRO - The Egyptian army has captured six people it regards as "terrorists" in Sinai after an attack on a police station earlier this week that killed 16 border guards near the border with Israel, a military source told state media. Egypt sent hundreds of troops and armored vehicles into North Sinai on Thursday to tackle militants operating near the border in an offensive commanders said had killed up to 20 people they deemed terrorists. The action, which Cairo says is its biggest military operation in the desert region since its 1973 war with Israel, is seen as crucial to maintaining stable relations between the former foes who signed a peace treaty in 1979. Israel fears militants based in the increasingly lawless region could link up with Palestinian jihadis in the neighboring Gaza Strip to launch attacks on the Jewish state - potentially jeopardizing the peace accord. The military source told state television that six militants had been captured in the border settlement of Sheikh Zuwaid, where on Wednesday Egyptian warplanes fired rockets at suspected militant hideouts. Separately, an army official told the al-Ahram state newspaper that preparations were underway to raid the mountainous Jebel El Halal region in Central Sinai in order to purge it of "terrorist" elements. A Reuters witness said several army tanks were heading towards al-Arish on Friday, the main administrative centre in North Sinai. In the past two days, the witness had only seen armored vehicles mounted with machine guns in the region. A security source in North Sinai told Reuters that seven and not six men had been detained, but that figure could not be immediately corroborated. He said the detained men had been previously arrested after bombings in resorts along Sinai's southern Red Sea coast between 2004-2006 that killed or wounded hundreds of foreign tourists. They had been jailed for months, he said, but were freed without charges.