The United States has started evacuation from an air base in Pakistan on Sunday at the order of the Pakistani government to leave the air base before December 11, reported local Urdu TV channel Geo.

According to the report, the evacuation kicked off Sunday morning when a US plane arrived at the Shamsi air base to take the US personnel back.

They started loading the luggage and equipment when the plane arrived, the reported quoted unidentified sources as saying.

In order to ensure the safe evacuation, security around the air base has been beefed up, said the sources.

The evacuation came eight days after the Pakistani government ordered the US to vacate its air base in the Shamsi area in Pakistan's southwest Balochistan province within 15 days following a NATO cross-border air strike at two Pakistani army check posts in Mohmand tribal area near the Afghan border on November 26, which killed 24 Pakistani troops and wounded 13 others.

Shamsi air base is located some 320 km southwest of Balochistan 's capital city Quetta. The US has reportedly been using the air base since 2001 for military operations in Afghanistan and drone strikes in Pakistan's northwest tribal areas bordering Afghanistan, a place that the US side believes to be a haven for militants who often launch cross-border attacks on the NATO troops in Afghanistan.

To order the US to vacate the Shamsi air base is one of the three steps taken by the Pakistani government in retaliation for the November 26 NATO incident, which the Pakistani government described as a blatant violation of its sovereignty.

The other two steps include closure of two border checkpoints for NATO supplies entering Afghanistan from Pakistan and boycott of the December 5 Bonn Conference on Afghan issue.

Following the decision to order the US to vacate the Shamsi air base within 15 days, the UAE foreign minister paid a visit to Pakistan, persuading the Pakistani President Asif Ali Zardari to reconsider the decision or to postpone the vacation deadline until NATO has completed its investigation into the November 26 incident, but the request was turned down by the Pakistani president.

Regarding the boycott of Bonn Conference, the Pakistani Prime Minister Yusuf Raza Gilani has rejected the requests both from the German Chancellor Angela Merkel and the US Secretary of State Hillary Clinton to reconsider the boycott decision. Prior to this, the Pakistani prime minister has also rejected the request by the Afghan President Karzai to reconsider the boycott decision.

The three steps so far taken by the Pakistani government has not brought an even official apology from the US and NATO apart from condolences and promise of investigation into the incident.

More steps could be taken by the Pakistani side as it has threatened to reconsider the overall arrangement with the US, NATO, ISAF in the fight against terrorism, said local watchers.