(Update 2: Mon 08/09/14 20:44:36)

MOSCOW (Sept 08): Russian stocks and the rouble extended losses on Monday afternoon, after the European Union announced new sanctions over Russia's actions in Ukraine despite Friday's peace deal between Kiev and separatist rebels.

At 1430 GMT, the dollar-denominated RTS index was down 1 percent at 1,245 points, and its rouble-based peer MICEX was 0.5 percent lower at 1,467 points.

The rouble was 0.56 percent weaker against the dollar at 37.13. It also lost 0.54 percent to 48.10 versus the euro and 0.56 percent to 42.06 against the dollar-euro basket.

Russian assets had been down in the morning as the sanctions were anticipated, but stock indexes nevertheless added around 0.5 percent to their losses after the new sanctions were unveiled.

As expected the sanctions target lending to major state oil firms including Rosneft, Gazprom Neft and pipeline operator Transneft

Rosneft was down 1.9 percent, Gazprom Neft down 2.6 percent, and Transneft down 1.8 percent.

However, the falls in Russian stocks were broad-based, including companies not included in the latest sanctions. Gas group Gazprom was down 1 percent and Sberbank down 1.7 percent.

EU leaders agreed the new sanctions on Friday, deciding to proceed with them despite the peace deal between Ukraine and separatist rebels, diplomatic sources told Reuters.

"A ceasefire must hold for sanctions to be lifted," a senior EU diplomat said on Friday.

Russia's Prime Minister Dmitry Medvedev said in an interview published on Monday that Russia would respond "asymmetrically" to any new western sanctions, including possibly a ban on European airlines crossing Russia.

Ukraine and pro-Russian rebels reached a ceasefire agreement on Friday, but fighting flared over the weekend in eastern Ukraine, jeopardising the deal.

The OSCE security watchdog said on Monday that "overall the ceasefire held though it is still shaky".

"The market does not fully believe that military actions have ceased ...in Ukraine, as there have been previous attempts to call a ceasefire but the truce had not lasted long," Natalia Samoilova, head of analyst at Golden Hills-Kapital investment house in Moscow, wrote in a note.

ING analyst Dmitry Polevoy said that investors were unnerved by comments from east Ukrainian rebels in which they reiterated demands for independence from Kiev despite Friday's peace deal.

The rouble was also coming under pressure because of falling oil prices, Polevoy added.

Brent fell below $100 per barrel on Monday, having shed over $2 since Friday morning, following an unexpected fall in Chinese imports which suggests China's economy is weak.

Other market participants emphasised the continuing threat of further Western sanctions.

"The conclusion of a truce hasn't lowered the pressure from western countries, and in some directions we are seeing it strengthening. In this situation the rouble is quite vulnerable," commented Igor Zelentsov, senior trader at Globex bank.