A US drone attack Sunday killed at least seven militants in Pakistan, officials said, days before the country's intelligence chief visits Washington with the contentious raids likely to be discussed. Attacks by unmanned American aircraft are deeply unpopular in Pakistan, which says they violate its sovereignty and fan anti-US sentiment, but US officials are said to believe the attacks are too important to give up. Drone strikes are likely to be a major issue when Pakistan's spymaster, Lieutenant General Zaheer ul-Islam, holds talks in Washington on August 1-3 with his CIA counterpart. In Sunday's attack, the second in the month of Ramadan, missiles struck a compound in Khushhali Turikhel village of the troubled North Waziristan tribal district, which lies on the border with Afghanistan. "US drones fired six missiles into a militant compound. At least seven militants were killed," a security official told AFP. "It is not immediately clear if there was an important militant killed in the attack." The toll might rise as militants search for colleagues buried under the rubble of the compound, the official said, adding that missiles also hit and destroyed two militant vehicles. Local intelligence officials confirmed the attack and casualties. Khushhali Turikhel lies around 35 kilometres (20 miles) east of Miranshah, the main town of North Waziristan which is considered a stronghold of Islamist militants. Washington regards Pakistan's semi-autonomous northwestern tribal belt as the main hub of Taliban and Al-Qaeda militants plotting attacks on the West and in Afghanistan. Ten militants were killed on Monday in a similar attack in Shawal area of North Waziristan. In a drone attack at the start of July, six militants were killed and an attack on June 4 killed 15 militants, including senior Al-Qaeda figure Abu Yahya al-Libi. There has been a dramatic increase in US drone strikes in Pakistan since May, when a NATO summit in Chicago could not strike a deal to end a six-month blockade on convoys transporting supplies to coalition forces in Afghanistan. On July 3 however, Islamabad agreed to end the blockade after the United States apologised for the deaths of 24 Pakistani soldiers in botched air strikes last November. Islam's trip on Wednesday marks the first Washington visit in a year by the head of Pakistan's Inter-Services Intelligence and signals a thaw in relations beset by crisis since US troops killed Osama bin Laden near Islamabad in May 2011. In protest at US drone attacks, local Taliban and Pakistani warlord Hafiz Gul Bahadur have banned vaccinations in North and South Waziristan, putting 240,000 children in the region at risk. They have condemned the immunisation campaign as a cover for espionage. In May, a Pakistani doctor was jailed for 33 years after helping the CIA find bin Laden using a hepatitis vaccination programme as a cover.