(Adds share price reactions, analyst comment)
LONDON Aug 8 (Reuters) - Oil company Afren has suspended output at its Barda Rash oilfield in Iraqi Kurdistan, the first field to shut in the region as Islamist militants advance closer, weighing on shares of London-listed oil producers active there.
"Afren has taken the precautionary step to temporarily suspend operations at the Barda Rash field," the company said in a statement, adding it was withdrawing all non-essential staff from the field.
Shares in Afren opened 7 percent lower on Friday, while Gulf Keystone Petroleum was down 2.6 percent and Genel traded 5 percent lower at 0712 GMT.
Oslo-listed oil producer DNO defied the trend, gaining nearly 3 percent as its shares reacted positively to a U.S. pledge to defend the Kurdish capital Arbil.
"There is a concern that DNO and Genel may follow suit, but both have much more material operations in the country than Afren," said Sanjeev Bahl, analyst at Numis.
U.S. oil majors Chevron and Exxon Mobil said on Thursday they were evacuating some staff from Kurdistan.
Gulf Keystone said it had increased security at its flagship Shaikan field, Iraqi Kurdistan's largest, but added that production and trucking operations were continuing safely.
Barda Rash, which is 60 percent owned by Afren, was producing a gross average of 785 barrels per day (bpd) of oil in the first quarter, making it a relatively small field.
Afren's other operations in Kurdistan continued to function normally but the company said it was closely monitoring events on the ground.
Barda Rash is Afren's only producing oil asset in Iraqi Kurdistan.
The oil explorer said the suspension of production at Barda Rash was not expected to have a significant impact on the company's cashflow.
On Thursday, some oil companies active in Iraqi Kurdistan saw double-digit share price declines as investors weighed the risk of possible production losses. (Reporting by Karolin Schaps in London; additional reporting by Sudip Kar-Gupta in London and Balazs Koranyi in Oslo; editing by William Hardy and Dale Hudson)