China has raised the threshold for a tax on crude oil charged to the nation's two biggest producers, the firms said, helping ease their financial burden and encourage output.

The Ministry of Finance hiked the minimum level for the levy to $55 per barrel, up from $40, PetroChina and the China Petroleum & Chemical Corp (Sinopec) said in statements late Thursday.

The move was retroactive to November 2011, they said.

Analysts said the move would help the corporate earnings of the companies and encourage oil production.

"It's time for the government to boost companies' enthusiasm for production," Wu Dazhong, an analyst at Shenyin Wanguo Securities, told AFP.

"This will definitely lift their stock prices, since investors believe the new policy will bring better corporate earnings," he said.

Investors cheered the news on Friday.

PetroChina was up 1.0 percent at 7.40 yuan in Shanghai by midday. Sinopec initially gained nearly two percent, but was down 0.3 percent to 7.40 yuan by midday.

In Hong Kong trading, PetroChina gained 2.5 percent to HK$10.64 by midday while Sinopec was up 1.9 percent at HK$8.81.

The new tax ranges from 20 to 40 percent of the price of a barrel of oil that costs more than $55.

China retail sales up 17% in 2011: ministry
Shanghai (AFP) Jan 6, 2012 - China's retail sales rose an estimated 17 percent year-on-year to 18 trillion yuan ($2.86 trillion) in 2011 as the government sought to boost domestic consumption, the Commerce Ministry said.

The country's retail sales were forecast to grow more than 14 percent annually in 2012, the ministry said, according to a report by the official Xinhua News Agency late Thursday.

China's National Bureau of Statistics is expected to issue official figures next week.

Wang Bin, deputy head of the ministry's market and consumption department, said retail sales were supported by rising incomes.

Chinese leaders have sought to engineer a shift to domestic consumption as exports -- a key driver of the economy -- slow due to turmoil in the key US and European Union markets.

Separately, the Ministry of Commerce said growth in foreign direct investment in China slowed sharply in 2011 amid world economic turmoil, rising 9 percent year-on-year to $115 billion, the China Daily newspaper reported Friday. Foreign investment rose more than 17 percent annually to $105.7 billion in 2010.

China said last week it will ease restrictions on foreign investment in some sectors while lifting caps on the proportion of foreign capital in others.

At the same time, however, the government said it will "withdraw support" for foreign investment in auto manufacturing to encourage the domestic industry in the world's largest car market.

Analysts said the move was unlikely to force global auto firms to leave the country, but it would make it harder for new foreign carmakers to enter.