Afghan government troops and Moslem rebel forces fought near Kabul yesterday in what U.S. officials said appeared to be a Pakistani-inspired rebel offensive motivated in part by fears that the United States may soon cut its aid to the guerrillas.

News agency and broadcast accounts from Kabul said the government sent planes to bomb locations southeast and west of the capital and fired heavy artillery and medium-range battlefield rockets from army bases in the city, rattling buildings there. Afghan officials and rebel sources said the fighting arose from an offensive by an Islamic fundamentalist rebel faction, the Hezb-i-Islami (Islamic Party) of Gulbuddin Hekmatyar.

Hekmatyar's forces began Wednesday to mount heavy attacks on security posts guarding approaches to Kabul from adjacent Logar and Wardak provinces, according to Abdul Ghafoor Jawshan, the Afghan government's charge d'affaires in Washington. A spokesman at the Hezb-i-Islami office in New York declined to confirm that any major offensive was underway, saying simply that "we are always fighting" against the government.

There were no details of the fighting available yesterday, although Agence France-Presse quoted a foreign military attache in Kabul as saying government casualties had been heavy. The government said it had killed 70 rebels in the first day of fighting.

Some rebel officers in Pakistan and U.S. officials in Washington expressed fears that Hekmatyar's faction and Pakistan's military intelligence agency, Inter-Services Intelligence (ISI), were risking heavy civilian casualties and ultimate defeat in the drive on Kabul. According to one source, who asked not to be identified, the United States has warned Pakistan that it opposes any action that would cause civilian casualties or tend to support one rebel faction at the expense of others.

For more than a decade during which the United States covertly has sent weapons to the antigovernment resistance fighters, or mujaheddin, ISI has handled their distribution and supervised the operations of the seven rebel groups permitted to operate from Pakistani territory. The Pakistani agency has worked for years to strengthen Hekmatyar, in hopes that he might ultimately take power and provide Pakistan with continuing influence over Afghan affairs, according to independent analysts, most mujaheddin and some U.S. officials.

Mujaheddin sources quoted in Pakistan and U.S. officials expressed fears that the apparent offensive on Kabul could repeat what was the rebels' worst military and political defeat in recent years -- an unsuccessful attempt to capture the eastern city of Jalalabad in the spring of 1989. In that battle, which came shortly after the Soviet Union ended its eight-year occupation of Afghanistan, ISI ordered the mujaheddin to attack the city under the leadership of Hekmatyar's forces, but the guerrillas resisted ISI direction, and the offensive turned into an uncoordinated and costly defeat that ravaged the city and its civilian population.

During the 20 months since the Soviet withdrawal, the mujaheddin have been unable to build a broad political coalition or unified military force -- partly, according to independent analysts, because of ISI's insistence on a leading role for Hekmatyar and other fundamentalist groups. As U.S. frustration with the continued stalemate has grown, Washington has reduced its military aid to the guerrillas and has sought a political solution to the conflict in talks with Moscow.

In recent months, the Bush administration requested a reduced allocation for military aid to the guerrillas for the 1991 fiscal year -- and Congress's intelligence committees have recommended further cuts. ISI "sees that lack of support in Congress and the moves {with the Soviets} toward reconciliation, and they are afraid that the aid to the mujaheddin is going to be cut off in the coming year," said a U.S. official. "They feel a new sense of urgency to get some progress on the ground" in hopes of reviving U.S. support, he said.

Mujaheddin last week captured Tarin Kot, capital of Oruzgan Province in central Afghanistan, their first such success since last year. The victory came after ISI delivered an ultimatum to the guerrillas demanding a military advance.

Rebel field commanders who oppose ISI management of their war this year formed a National Commanders' Council to attempt military coordination independent of Pakistan. In the past 10 days, these Afghan nationalist commanders and ISI each have met near the Pakistani-Afghan border with Ahmad Shah Massoud -- the country's most powerful rebel commander, who controls much of northeastern Afghanistan -- in an apparent attempt to win his support.