The Kenyan military has said its warplanes bombed targets held by al-Qaeda-linked armed group al-Shabab in Somalia, in retaliation for an attack on a Nairobi mall that killed at least 67 people.

The Kenya Defence Forces said on Thursday that they had destroyed a training camp used by the members of the al-Shabab group who attacked the Westgate Mall on September 21.

"This was part of a broader mission by the AMISOM [the UN-backed African peacekeeping mission in Somalia], targeting where the Shabab were training," Colonel Cyrus Oguna, a spokesman for the Kenyan military, told Reuters.

“Those attackers at the Westgate did their training there. We have been monitoring this particular area over a period of time, and we moved in when we got the green light."

The camp had more than 300 fighters, many of whom are believed to have been killed or injured, the KDF said in a statement.

Oguna said raids on the rebel strongholds would be sustained.

Kenya's military said the "major aerial offensive" in the Dinsoor region completely destroyed the training camp at Hurguun and at least four "technicals" - improvised fighting vehicles - and a weapons store.

Two leading members of al-Shabab were killed on Monday in a Kenyan drone strike.

However, al-Shabab denied there had been any attack.

"We do not know where they [Kenyan army] are getting that from. No attack happened in our area. Not in Dinsoor, not anywhere else," an al-Shabab spokesman told Al Jazeera, adding that the group's fighters had attacked Badhaadhe and Kismayo in the Jubba regions in the south.

Meanwhile, a top UN official has said that the war against al-Shabab fighters in Somalia has “ground to a halt” and needed a surge of almost 4,400 more African Union troops and massive UN assistance to break the stalemate and avoid failure.

Deputy Secretary-General Jan Eliasson told the Security Council on Wednesday that the UN-endorsed African Union force now in Somalia, and the Somali military, lack “the capacity to push beyond areas already recovered” from al-Shabab in the last 18 months.

Source: Al Jazeera and agencies