BEIJING, April 8 (Reuters) - Several Chinese state

holding companies vowed on Tuesday to increase share investment

while a slew of listed companies announced share buybacks as

Beijing stepped up efforts to stabilise a stock market rocked

by U.S. tariff woes.

The announcements by China Chengtong Holdings Group

and China Reform Holdings Corp come a day after

state fund Central Huijin said it would increase share holdings

to steady markets.

China's stock benchmark rebounded in early trade on

Tuesday, clawing back some of the 7% plunge from Monday, which

was fuelled by trade war and global recession fears.

Washington last week imposed extra tariffs of 34% on China,

which then fired back with its own 34% levies on U.S. imports.

Chengtong said its investment units would increase holdings

in stocks and exchange-traded funds (ETFs) to safeguard market

stability.

"We are firmly optimistic toward the growth prospects of

China's capital markets," the state investment firm said in a

statement, vowing to support high-quality growth of Chinese

listed companies.

China Reform Holdings Corp, also known as Guoxin, said in a

separate statement that an investment unit will increase

holdings in tech companies, state firms and ETFs, tapping a

relending scheme for share buybacks. Initial investment will be

80 billion yuan ($10.95 billion).

Another state holding company, China Electronics Technology

Group, said it would boost share buybacks in listed units to

bolster investor confidence.

Meanwhile, a growing number of listed companies unveiled

plans to buy back shares.

Oil giant Sinopec said its state-owned parent

plans to buy its China- and Hong Kong-listed shares worth at

least 2 billion yuan over the next 12 months to demonstrate

"confidence in future growth prospects."

Orient Securities said it is studying plans to

buy back shares in a bid to express optimism and actively

protect shareholder interest.

Other listed firms that unveiled share buy-back plans

include Intco Recycling Resources Co and Spring

Airlines Co. China Pacific Insurance (Group) said it

would contribute to market stability by increasing investment in

strategic sectors.

State fund Huijin said on Tuesday it has ample liquidity and

smooth financing channels to help it suppress abnormal market

volatility in its role as market "stabiliser".

"Central Huijin has adequate confidence and competence to

resolutely maintain smooth operation of the capital market,"

Huijin said in a statement.

"We will act decisively when needed."

Separately, China's central bank said on Tuesday it

supported Central Huijin Investment increasing its holdings in

stock funds.

($1 = 7.3081 yuan)