* Mounting Ukraine tensions cap gains in copper
* Nickel on track for 11th weekly increase in 12
(Adds comments, updates prices)
SINGAPORE, April 25 (Reuters) - London copper futures hit a seven-week high on Friday and were headed for their best week in about a month on firm demand in top market China, although growing tensions in Ukraine curbed further gains.
Premiums for spot copper in China have surged to levels last seen in 2010 amid strong seasonal demand this month. April and May are typically brisk consumption months for copper due to increased construction activity.
But copper futures struggled to push higher due to mounting violence in Ukraine, which is capping investor appetite for some risky assets from commodities to equities.
Ukrainian forces killed up to five pro-Moscow rebels as they closed in on the separatists' military stronghold in the east, and Russia launched army drills near the border in response, raising fears its troops would invade.
Three-month copper on the London Metal Exchange was nearly flat at $6,755.75 a tonne by 0301 GMT after earlier hitting a high of $6,775, its strongest level since March 7.
For the week, copper was up 1.5 percent, its biggest such gain since the week ended March 28.
The escalating tensions in Ukraine are prompting some investors to lock in recent gains in copper, although the metal may still scale higher in the near term given the strength of seasonal demand in China, said Helen Lau, senior metals analyst at UOB-Kay Hian Securities in Hong Kong.
"If you ask fabricators, their order books are all pretty good," Lau said, adding that copper prices may bounce back in the short term to $7,000, a level last seen in early March.
The most-traded July copper contract on the Shanghai Futures Exchange rose 1.7 percent to 47,760 yuan ($7,600) a tonne.
Purchases by China's state stockpiler, the State Reserves Bureau (SRB), had helped boost premiums for copper held in Shanghai's bonded warehouses to $95-$115 a tonne over cash LME from as low as $65 in early April, said Lau.
The SRB has bought at least 200,000 tonnes of imported copper stored in bonded warehouses after global copper prices dived to multi-year lows in March.
London nickel was little changed at $18,340 a tonne after fears of tighter supply lifted prices to $18,600 on Thursday, its highest in more than 14 months.
Nickel, the best performing base metal this year, has gained 32 percent so far in 2014 as an Indonesian ban on exports of unprocessed minerals from January tightened supplies of nickel ore which top buyer China uses in the production of stainless steel.
For the week, nickel was up more than 2 percent, its 11th weekly gain out of 12.
Three month LME copper
Most active ShFE copper
Three month LME aluminium
Most active ShFE aluminium
Three month LME zinc
Most active ShFE zinc
Three month LME lead
Most active ShFE lead
Three month LME nickel
Three month LME tin
($1 = 6.2489 Chinese yuan)
(Editing by Himani Sarkar)