Three suicide bombers attacked a guesthouse used by foreigners in the northern Afghan province of Kunduz yesterday, killing four Afghan security guards employed by a German company, a senior police detective said. The raid came on the second day of the Muslim fasting month of Ramadan and 13 months after Taleban suicide bombers and gunmen stormed a US contracting company office in Kunduz, killing five, including three foreigners. The once peaceful north of the country has seen a series of high profile attacks and assassinations over the last year, including the killing of a top police commander in May. One attacker detonated a car bomb at the gates of the guesthouse. The other two stormed the building where they fought Afghan forces for a couple of hours before detonating their explosives, said Kunduz police detective Abdul Rahman. Ten people, including civilians and a police officer, were wounded in the early morning attack, said Rahman . No foreigners were among the wounded, he said. The Taleban claimed responsibility for the attack, said spokesman Zabihullah Mujahid. The attack came as the US military has speculated whether Taleban leaders would take a break during Ramadan and cross back over the border into Pakistan. A Western official in Kabul predicted on Sunday limited spikes in violence, including some high profile attacks during Ramadan. Rahman said the slain Afghan security guards worked for a local security company, which was employed by German development agency GIZ, formerly called GTZ. The guesthouse was run by the local security company and sometimes accommodated foreign staff, he said. "According to our knowledge it wasn't an attack against GIZ, it appears to be an attack against the local security firm," said Hans Spehling, a spokesman for GIZ, adding that all GIZ employees were safe. He also confirmed the local security firm was employed by GIZ. Violence has intensified in the north of the country in the past year as insurgents seek to demonstrate their reach beyond their traditional southern heartland around Kandahar city. On July 2, 2010, Taleban attackers made a pre-dawn attack on the newly opened offices of Development Alternatives Inc (DAI). The police chief of north Afghanistan, General Dawood Dawood, was killed in May this year in a massive bomb attack in Takhar province, along with the Takhar police chief. In June, a suicide bomber detonated his explosives at a memorial service for Dawood in Kunduz, killing at least four policemen. The attack appeared to target the police chief of Kunduz province, Sameullah Qatra, whose predecessor in the post was killed by a suicide bomber in March. Qatra was unharmed. Violence is at its worst in Afghanistan since US-backed Afghan forces toppled the Taleban government in late 2001, with high levels of foreign troop deaths, and record civilian casualties. A gradual transition of security control to Afghan forces began last month with when areas were handed over by the NATO-led International Security Assistance Force. Afghan forces are due to take full control across the country by the end of 2014. In the past month insurgents have carried out a string of destabilising assassinations of high-profile southern leaders, including President Hamid Karzai's younger brother, and several large attacks killing police and civilians.