Despite repeated promises that they will eventually withdraw, Chinese forces were reported to be pushing deeper into Vietnam today as fighting appeared to be accelerating in some places.

Radio Hanoi and foreign analysts reported engagements near Langson, as well as in the areas around Caobang and south of Laocai, where Chinese units are said to be moving south on both sides of the Red River.

Pro-Peking sources here and a Japanese news agency said today that the Chinese have killed or wounded at least 17,000 Vietnamese soldiers and taken many prisoners in their 11-day-old invasion now said in places to be as deep as 20 to 25 miles inside Vietnam.

Analysts in Bangkok said Chinese troops that have been engaged in skirmishes and some artillery and tank duels near Langson now appear to be moving to try to capture the city about 85 miles northeast of Hanoi.

But the analysts emphasized that it was difficult to tell exactly what was happening in the area and they did not know if the Chinese had yet clashed with the city's defenders. They also said that the casualty figures seem exaggerated as did Hanoi's earlier claims that 18,245 Chinese troops and been killed or wounded through yesterday.

Most civilians in Langson, which was visited by Rep. Elizabeth Holtzman (D-N.Y.) last week, were evacuated days ago and there was speculation the Vietnamese might fall back rather than risk a full-scale clash. Reuter quoted Japanese Foreign Ministry sources as saying Vietnamese troops had withdrawn temporarily from Langson and were shelling the advancing Chinese from surrounding hills.

The official New China News Agency reported a Vietnamese battalion invaded a Chinese border area north of Langson, burning down two villages and a tract of forest in three days of raids that began Thursday. The agency said 68 Vietnamese were killed and one captured by Chinese defenders.

[Japan's Kyodo News Service quoted Peking Radio Wednesday morning saying that Vietnamese forces made three assaults into China on last Thursday, Friday and Saturday, Washington Post correspondent William Chapman reported from Tokyo. According to the Chinese in the first attack the Vietnamese shelled a commune inside Kwangsi Province, in the second attack 60 Vietnamese saldiers attacked a Chinese production brigade and in the third attack a full battalion of Vietnamese troops burned two Chinese villages. The Chinese radio reported that 30 Chinese were killed or wounded in the attacks and 68 Vietnamese were killed.]

The capture of Vietnamese prisoners of war, which the one Chinese source claimed now numbered in the thousands, was described by a Hong Kong source with close ties to Peking as an important objective of China's continuing operation inside Vietnamese territory. The source said, "We want to bring them back to reason" and weaken their hostility to China through good treatment and polite discussions of China's side in the border dispute.

The first official Chinese pictures of Vietnamese prisoners, printed in Hong Kong's pro-Peking newspapers this morning, appear to show Vietnamese prisoners playing chess, receiving clothing and being treated by a doctor.

Analysts here and in Bangkok, as well as travelers recently returned from Vietnam, said Vietnamese troops appeared to be confident of victory against the Chinese and eager to fight. But the analysts said Vietnamese troops fighting pro-Peking insurgents in Cambodia appeared to be in difficulty, particularly in western Cambodia far from Vietnamese sources of supplies.

U.S. Deputy Secretary of State Warren Christopher, at a Bangkok press conference, supported the idea of an international conference on Cambodia. The Sino-Vietnamese dispute over the small country has helped cause their border clash.

The Kyodo news agency, quoting what it said were Chinese sources in Peking, said unpublished official reports circulating in China reported 7,000 Vietnamese casualties in the first week of fighting across from China's border province of Yunnan and 10,000 Vietnamese casualties in only the first two days of fighting across from China's Kwangsi Chuang autonomous region.

Unofficial reports of large numbers of Vietnamese casualties would help China show it was fulfilling its objective to "punish" Hanoi for previous border raids into China. Releasing such casualty figures officially, however, would seem to be an attempt to "humiliate the Vietnamese people," said a source here with ties to Peking.

The Kyodo news agency president, Takeji Watanabe, yesterday interviewed Chinese Vice Premier Teng Hsiao-ping in Peking although the casualty report was not attributed to Teng. The Kyodo report said the Chinese documents said "several thousand" Vietnamese had been taken prisoner.

It said Chinese troops were operating under instructions forbidding advances beyond 50 kilometers, or 31 miles, into Vietnamese territory. The reports said fighting in general was going on within 12 miles of the border. They said three Vietnamese missile launching installations had been destroyed and four others rendered useless.

A Hong Kong source said today the Chinese had also destroyed trenches, minefields, pillboxes and other installations in order to make it easier to reenter Vietnam if Hanoi provocations forced another invasion.

Like the sparse official Chinese reports on the invasion, documents cited by Kyodo gave no Chinese casualty figures. They said, however, that the family of each Chinese soldier killed in action would receive about $2,000 from the government. They said Chinese troops were often fighting in small combat teams, to counter guerrilla tactics used by the Vietnamese.

The Vietnamese haven not reported their own casualties. They briefly showed two apparent Chinese prisoners to foreign journalists, but have not said how many Chinese have been captured.

The Vietnamese army paper Quandoi Nhandan today reacted angrily to Chinese press reports praising Chinese "kindness" toward Vietnamese in the battle area. The newspaper questioned why the New China News Agency "cooked up" these stories "while hundreds of thousands of Chinese troops are destroying Vietnamese homes and killing Vietnamese people."

One Chinese agency report said troops had "recovered" an area of mountains north of Caobang, indicating Peking may attempt to hold onto territory it did not control before the Feb. 17 invasion. Then, the agency said, the Chinese company that took the area moved into neighboring Vietnamese villages and "immediately set to work, sweeping courtyards and repairing roads."

Another Chinese report said.Vietnamese forces ransacked houses and shops in one of their own towns before retreating in the face of a Chinese onslaught.

Analysts here said Chinese actions appeared to be confined generally a 20-mile-deep strip along Vietnam's frontier. Peking appears to want to destroy as many fortifications, and as many mainforce Vietnamese army units, as it can, according to these analysts.

But Hanoi has so far kept most of its regular troops away from the fighting. Militia and regional army forces, well equipped but not as experienced as mainforce troops, have conducted most of the fighting with some mainforce troops brought up to fill in gaps, the analysts said.

An editorial in China's official People's Daily renewed an appeal for negotiations with Hanoi to settle the border dispute. It said a statement by Vietnamese Vice Foreign Minister Nguyen Co Thach rejecting talks showed the Vietnamese "will doggedly continue to make armed provocations and create tension in China's border areas for a long time to come."

It said Vietnam had committed "3,535 armed provocation incidents on the Chinese border from 1974 to mid-February this year" and the problem could "only be settled through negotiations between the two sides."