More than 100 Afghan troops were killed in an offensive aimed at slowing the buildup of U.S.-backed Moslem rebels west of the capital of Kabul, Western diplomats said Tuesday.

One diplomat said the Indian Embassy had begun evacuating personnel from Kabul, in apparent contradiction of Prime Minister Rajiv Gandhi's assertion that the Soviet-backed government had a good chance of survival.Another diplomat said Afghan troops launched a three-day operation last week against "increasingly strong mujahideen (ebel) concentrations" in the Paghman area, a few miles west of Kabul.

More than 100 Afghan troops died in the offensive, the diplomat said. He said rebel casualties were unknown, "but given the intensity of the fighting, presumably were high."

Both Western diplomats said Soviet and Afghan aircraft bombed rebel supply routes to the area, killing three civilians, and artillery units shelled the Paghman hills, from where the rebels frequently launch rockets against Kabul.