LONDON — WikiLeaks declared victory Thursday in the first round of its campaign against the financial blockade imposed by Visa and MasterCard after an Icelandic court ordered their local partner to resume processing credit card donations to the secret-spilling site.

Visa and MasterCard were among half a dozen major U.S. financial firms to pull the plug on WikiLeaks following its decision to begin publishing about 250,000 State Department cables in late 2010.

WikiLeaks says that the ensuing blockade has led to a 95 percent fall in revenue, something which founder Julian Assange says has forced him to focus on fundraising at the expense of his site’s publication work.

The judgment, handed down by Reykjavik District Court, is “a very important milestone in our campaign,” WikiLeaks spokesman Kristinn Hrafnsson said in a telephone interview. Lawsuits remain active in Denmark and in Belgium, he said, but the Icelandic win was “a small but very important step in fighting back against these powerful banks.”

The District Court ordered Visa and MasterCard’s local partner, Valitor, to resume funneling donations to WikiLeaks’ payment processor, DataCell, within two weeks or face 800,000 kronur (about $6,000) in daily fines, according to DataCell lawyer Sveinn Andri Sveinsson.

The implications of the judgment, which Valitor plans to appeal, weren’t immediately clear.

Even if Valitor is eventually forced to comply with the judgment, it isn’t clear whether Visa or MasterCard would allow their customers to make donations to DataCell or WikiLeaks. Both companies have refused to deal with WikiLeaks for the better part of two years, leading to allegations that they had bowed to U.S. pressure to starve the organization of funds.

Neither Visa Inc. nor MasterCard Inc. immediately returned emails seeking comment on the judgment.