A woman has died after a grenade attack in the Kenyan port city of Mombasa, police said Wednesday a day after armed men opened fire and threw explosives into a restaurant. \"We lost one of the victims, a lady who was a security guard at the club, she died in hospital,\" regional police chief Aggrey Adoli told AFP. Three others wounded in the attack are still in hospital, one in a serious condition, following the attack by gunmen late Tuesday. One gunman opened fire when guards at the restaurant prevented him and two accomplices from entering the Bella Vista restaurant, before the attackers hurled two grenades and fled, Adoli added. One of the grenades exploded near the entrance to the restaurant and the other near a car parked outside. \"I was having a drink nearby and then I saw people running after a loud blast,\" said witness Oscar Ndambuki, speaking shortly after the attack. Popular spot for tourists The restaurant sits on one of the most popular avenues in Mombasa and is a popular gathering spot for tourists. There was no immediate information on who was behind the attack. Since Kenya sent tanks and troops into Somalia late last year, a whole series of grenade attacks and explosions have taken place, both in Nairobi and in northern towns and camps housing Somali refugees close to the border. Targets have ranged from police vehicles to local bars to churches. The Kenyan authorities often blame such attacks on Somalia\'s Al Qaida-affiliated Shebab rebels. Last month the hardline Shebab warned Kenya of retribution and revenge attacks for joining the African Union force battling the insurgents. Earlier on Tuesday, a policeman was killed and two others seriously wounded when a landmine exploded beneath their vehicle as they escorted aid workers near the sprawling Dadaab refugee camp in northern Kenya.