ISLAMABAD – At least six people were killed on Friday evening as mortar shells fired from Afghanistan side hit Pakistan’s northwestern border area of South Waziristan, reported private TV channels.Quoting official sources, the channels reported that around 30 mortar shells were fired from Afghan side of the border landed in the Angoor Adda area of the South Waziristan, killing six people. The sources did not reveal the identity of the victims.It was not clear yet who fired these shells from the other side of the border.Two incidents of mortar shelling from Afghanistan were observed last December, killing at least one Pakistani and wounding five others in the tribal region of North Waziristan.In the past, such cross-border shelling escalated the tension between Pakistan and Afghanistan as the two countries accused each other of firing.In November last year, Pakistan lodged a formal protest with Afghanistan over cross-border shelling as Pakistan’s Foreign Ministry and the military said that Afghan National Army troops fired mortars into Pakistani territory.