Nairobi. Kenyan security forces have taken control of Nairobi’s Westgate shopping mall attacked by al-Shabab rebels, and are currently carrying out a final sweep of the building after all remaining hostages had been freed.Explosions and sporadic gunfire were heard coming from the shopping complex on Tuesday morning, hours after officials claimed Kenyan troops had wrested back "control” of the centre from the al-Qaeda-linked armed group. At least 62 shoppers and staff have been killed and close to 200 wounded in the siege that began on Saturday, but concerns are high that the toll may yet rise.The Somali-based al-Shabab movement said it had carried out the attack in retaliation for Kenyan military operations in Somalia."If you want Kenya in peace, it will not happen as long as your boys are in our lands,” rebel spokesman Ali Mohamud Rage said in a statement posted online.The fate of 63 people listed as missing remains unclear.However, Kenyan officials have said all the hostages are believed to have been freed, with the interior ministry saying on Tuesday that the four-day-long assault was "very near the end”.Security sources said "one or two” fighters were barricaded on one of the upper floors of the complex. Al-Shabab ‘not acting alone’In an interview on Monday, Kenya’s Foreign Minister Amina Mohamed told Al Jazeera that al-Qaeda, not al-Shabab, was behind the attack.Al-Shabab is "not acting alone”, this assault is "part of an international terrorism campaign”, Mohamed said. She said that about 20 gunmen and women were behind the attack, and that both the victims and perpetrators came from a variety of nationalities.In a separate interview with the American PBS network, Mohamed said "two or three” Americans and one Briton were among the attackers."Al-Shabab are looking for relevance on an international scale - especially after a change of leadership - and is looking to send the message that they are still a force to be reckoned with,” Al Jazeera’s Mohamed Adow reported from Nairobi.In a speech on Monday, the Somali president, Hassan Sheikh Mohamud, described al-Shabab as a threat to the world."They are a threat to the continent of Africa, and the world at large,” he said. Al-Shabab and al-Qaeda announced their alliance in February last year, and Abu Omar, an al-Shabab commander, confirmed in an interview with Al Jazeera that his group is taking orders from al-Qaeda.