LONDON, July 16 (Reuters) - Benchmark northwest European gasoline refining margins rose sharply on Monday after crude prices fell by more than 4 percent and trading activity rose.
* About 30,000 tonnes of Eurobob gasoline traded on barges on throughout the day on Monday in a wide price range as crude slumped.
* Brent prices reached a three-month low as Libyan ports reopened and traders eyed potential supply increases by Russia and other producers.
* New export demand on transatlantic routes emerged in recent days.
* Strong interest in recent weeks in shipping gasoline from Europe on transatlantic routes has been giving margins a floor.
* Total sold two barges of Eurobob gasoline to Shell at $682 a tonne fob ARA.
* Elsewhere, 26,000 tonnes of Eurobob gasoline traded in a range of $678-$707 a tonne fob Amsterdam-Rotterdam, compared with $691-$692 on Friday. Total, CCI, NIC and Gunvor sold to Shell, Mabanaft, Hartree, Finco, Trafigura and BP.
* There were no deals on barges of premium unleaded gasoline.
* No cargoes traded.
* The August swap stood at $682 a tonne at the close, down from $710.
* The benchmark Eurobob gasoline refining margin rose to $11.287 a barrel, from $8.268.
* Brent crude futures were down $3.28 at $72.05 a barrel at 1637 GMT.
* U.S. front-month RBOB gasoline futures were 4.48 percent down at $2.0123 a gallon.
* The U.S. RBOB refining margin RBc1-CLc1 was down 5.95 percent at $16.43 a barrel.
* Trafigura sold a cif NWE cargo to BP at $619 a tonne. (Reporting by Ahmad Ghaddar Editing by David Goodman)