* Athens reopens, slumps around 20 percent
* Other major European stock markets gain
* Markets buoyed by HSBC, Heineken results
* Weak China data weigh on mining stocks
By Sudip Kar-Gupta
LONDON, Aug 3 (Reuters) - European shares rose on Monday, shrugging off a slump by the Greek stock market when it reopened after closing for five weeks, as strong results from Heineken and banks supported the broader market.
The pan-European FTSEurofirst 300 index rose 0.5 percent and the euro zone's blue-chip Euro STOXX 50 index gained 0.4 percent. Germany's DAX advanced 0.5 percent and France's CAC 0.3 percent.
However, Athens' benchmark ATG equity index dropped by around 20 percent, led by shares in the country's major banks .
Trading was suspended in Athens in late June as part of capital controls imposed to stem an outflow of euros that threatened to collapse Greece's banks and hurl the indebted country out of the euro zone.
Since then, Athens and the European have agreed a bailout plan in exchange for stringent reforms and budget austerity. But implementation of the deal is some way off, keeping alive the threat of political and economic instability.
Nevertheless, the impact of Greece on the rest of Europe has been mitigated by economic stimulus measures from the European Central Bank, whose record-low interest rates and liquidity have helped prop up European equities.
"A lot of overseas investors have stopped paying too much attention to Greece," said Andreas Clenow, hedge fund manager and principal at ACIES Asset Management. "The ECB's measures are helping to limit the negative fallout from Greece."
Heineken shares rose 4.8 percent after the drinks company's second-quarter results beat expectations.
According to data from Thomson Reuters StarMine, 55 percent of companies listed on the European STOXX 600 index have beaten or met market expectations with their results so far this quarter.
The STOXX European 600 Banking Index also gained 0.4 percent. Shares in HSBC edged up after the bank reported higher first-half earnings and announced the sale of its Brazilian unit to Banco Bradesco SA for $5.2 billion. .
Commerzbank also advanced after the German lender reported higher profits.
Mining stocks fell, however, after weak economic data from China, the world's biggest metals consumer.
The data showed that China's factory activity shrank more than initially estimated in July.
Europe bourses in 2015: link.reuters.com/pap87v
Asset performance in 2015: link.reuters.com/gap87v
Today's European research round-up (Editing by Larry King)