(Reuters) - Two Taliban suicide bombers attacked an army bus and another army vehicle in the Afghan capital on Wednesday, killing at least seven people and wounding more than 15, the government said, a day after Afghanistan and the United States signed a long-delayed security agreement.

"An Afghan army bus and another car carrying Afghan army personnel were targeted by two suicide bombings," deputy interior minister General Ayoub Salanghi said in a statement.

The Taliban, fighting to oust foreign forces and the U.S-backed government, claimed responsibility for the attacks in the east and west of Kabul.

"Double martyrdom attack has rocked #Kabul city this morning amid current year's ongoing #Khaibar operation," the Taliban said on Twitter, referring to their yearly summer fighting offensive.

The attack in the west of the city, close to Kabul university, was the more serious of the two. It destroyed the army bus and shattered shop windows. At least seven were killed, the defense ministry said.

"I was walking down the road when a huge explosion occurred. Right after the blast, I saw dust and smoke rising from the area and then I escaped,” said shopkeeper Sanaullah Khan.

Officials from Afghanistan and the United States on Tuesday signed a deal allowing American troops to stay in the country after the end of the year, filling a campaign promise by new President Ashraf Ghani.