Afghan government radio said Thursday that 20 Pakistani and U.S. advisers were killed during a battle with government troops in Afghanistan's eastern Nangarhar province. A U.S. official denied the report.

In Moscow, the Soviet news agency Tass reported that Moslem guerrillas fired rockets Wednesday at the airport in Kabul, the Afghan capital, killing four people including a small child.The United States and Pakistan back the guerrillas. But the nations have denied sending personnel to Afghanistan to help the insurgents, despite repeated charges to the contrary by Afghanistan's communist government.

Radio Kabul, monitored in Islamabad, said 500 Pakistani military personnel also were killed in Wednesday's fighting near the eastern city of Jalalabad.

Maj. Robin Higgins, a Pentagon spokesman, denied that U.S. advisers were killed and said: "There are no Department of Defense advisers inside Afghanistan." He said in an interview in Washington that the only U.S. soldiers in the region are in Pakistan, where they are training guerrillas to neutralize lands mines in a program initiated by the United Nations.

Sources close to the guerrillas said fighting has been heavy around Jalalabad during the past several days.

A guerrilla spokesman in Pakistan, who requested anonymity, said Thursday that the insurgents had attacked Jalalabad's airport with long-range artillery.

Some guerrilla sources and Pakistan's official television said on Wednesday that the airport had fallen to the insurgents. Other guerrilla sources have contradicted those reports.

Jalalabad is 45 miles west of the Pakistan border and on the main highway linking the Afghan capital with Pakistan.

Radio Kabul said "hundreds of criminals" were killed by government troops protecting the city.