A roadside bomb targeting a border guard patrol near the Iranian border killed two soldiers Monday and injured another four, police said. The attack occurred shortly after dawn in the frontier town of Mandali, about 50 kilometers from the Iranian border in Diyala province northeast of Baghdad, a police officer said on condition of anonymity as he was not authorized to release information to the media. Diyala has become one of Iraq's most dangerous areas. Most of the activities of al-Qaida in Iraq have been pushed out Anbar province and Baghdad, into Diyala and the northern city of Mosul, following a surge of US troops in Baghdad and the work of Sunni tribal groups in Anbar who turned against al-Qaida. "Diyala has been one of the tougher fights," US Navy Rear Adm. Gregory Smith said in Baghdad Sunday. "Diyala is an area of significant interest for al-Qaida."