ISLAMABAD , Pakistan ( CNN ) -- Police tightened security at airports across Pakistan Thursday after receiving reports of a possible suicide attack at the international airport that serves Islamabad . Pakistan 's capital was rocked by a suicide attack on the city 's Marriott Hotel at the weekend . Officers emptied the parking lot at the Benazir Bhutto International Airport , on the outskirts of Islamabad , said Parvez George of the country 's Civil Aviation Authority . Flights were going out of the airport , but police cleared the terminal building of the large crowds that usually gather to see relatives arrive or depart , George said . Muhammad Asghar of Islamabad Police told CNN that authorities placed the airport on high alert after intelligence reports indicated it was under threat of an attack . The country 's capital city is on edge since a deadly blast Saturday night at the Marriott Hotel . The explosion killed more than 50 people , including two U.S. military personnel and the Czech ambassador to Pakistan . The bombing wounded more than 250 and sparked a fire that left the hotel in ruins . On Thursday , the Danish intelligence service said one of its employees , Karsten Krabbe , was among the victims of the blast . Krabbe , a 53-year-old married father of two , was a security adviser at the Danish Embassy in Islamabad , which was targeted by a suicide bomber in June . That attack killed six people and wounded more than 20 . `` Karsten Krabbe lost his life in a cowardly and ruthless terror attack , '' the Danish intelligence service said in a statement . Reacting to the Saturday 's attack , the U.S. government barred employees from major hotels in several Pakistani cities , the U.S. Embassy in Pakistan said . The Embassy in Islamabad added Lahore on Wednesday to a list of three other cities in which U.S. personnel are no longer allowed to visit or stay in major hotels . The Embassy took the measures because of general security concerns , said spokesman Lou Fintor Thursday . He did not comment on a specific threat . In addition to the hotel restriction , the Embassy temporarily suspended visa and other routine consular services for Thursday and Friday . It said it will make available emergency services for U.S. citizens who need passports or are arrested . And an advisory reminded Americans in Pakistan to avoid crowds and demonstrations and to keep a `` low profile . '' It said Americans should vary times and routes while traveling to avoid setting patterns . And it said a travel warning issued on August 7 still stands : U.S. citizens should defer nonessential travel to Pakistan due to continuing security concerns . -- CNN 's Zein Basravi and Reza Sayah , and Journalist Nasir Habib contributed to this report .
Benazir Bhutto International Airport on high alert . The airport is the main hub for international flights to and from Pakistan, but it has been closed since last week because of a bomb scare that was linked to al Qaeda in Pakistan. Officers combed through the airport compound looking for explosives . Danish intelligence says one of its employees was killed in Marriott hotel attack .