Vietnam accused China yesterday of carrying out armed intrusions into Vietnamese territory, claiming that an unspecified number of Chinese soldiers occupied strategic positions in Caolang Province.

"Late in the afternoon, thousands of Chinese were moved into the area, causing a very tense situation," a Vietnamese Foreign Ministry statement said. It said the Chinese were digging trenches in a gorge on Chonmu Mountain and that they opened fire on Vietnamese guards.

The statement distributed by the Vietnam News Agency said that Vietnamese border guards fought back in self-defense.

A Hanoi Radio broadcast monitored in Bangkok said a number of Vietnamese soldiers were wounded or killed.

In Peking, there was no government reaction to Vietnamese claims that a number of Vietnamese soldiers were killed in incidents along the Sino-Vietnamese border. Western diplomatic sources, while acknowledging increased tension along the border, suggested that a ull-scale armed conflict seemed unlikely.

Hanoi Radio also charged yesterday that China had sent at least 100,000 soldiers and advisers into Cambodia as part of an increased flow of war material to the Peking-backed government in Phnom Penh. Peking supports Cambodia in its border war with Vietnam.

The reported Chinese incursions into Vietnam's Caolang Province, about 135 miles north of Hanoi, came as senior Vietnamese leaders were visiting the Soviet Union. Communist Party chief Le Duan and Premier Pham Van Dong conferred with President Leonid Brezhnev, Premier Alexei Kosygin and other top Kremlin Officials.

Tass news agency said the talks were conducted in a "atmosphere of cordiality, comradely frankness and mutual respect." It said both sides "noted with concern negative" developments in the Far East and in Southeast Asia.