WASHINGTON - The United States saw some positive signs in Syria where the Arab League (AL) monitors are deployed, but those were not enough, a State Department official said on Thursday.

"We've seen a modest prisoner release, but it appears that the most important high-profile political activists have not been released. And we also want to see Syria opened to the press," State Department spokeswoman Victoria Nuland told reporters.

"So, unfortunately, violence continuing, the Syrian regime still propagating violence against its own people, but in some places where the monitors have deployed, we see some positive signs, but not enough," she said.

Nuland's comment came as AL observers visited on Thursday a number of neighborhoods in several provinces of Syria and met with many people there.

Syria signed the AL observer protocol on December 19 in Cairo after the regional bloc threatened to submit the issue to the United Nations Security Council.

The first batch of monitors, some 50 people, arrived in Syria late Monday, officially kicking off the AL's ground assessment of Damascus' compliance with an Arab peace plan to conclude the months-long domestic rift.

A new batch of Arab observers arrived in Damascus on Wednesday as their colleagues escaped gunfire in a restive neighborhood in central province of Homs, a flashpoint of the violence.

Nuland believed that the effectiveness of the AL monitors will depend on "how they execute their mission," urging them to be active and insist on their full access to Syrian people.

Similar to State Department spokesman Mark Toner's remarks on Tuesday, Nuland did not directly comment on the effectiveness of the AL monitors

"Our understanding is that the Arab League intended over a period of days and weeks to deploy somewhere between 150 and 300 monitors. So they're in the middle of that deployment now," she said.

"So I think we need to let them continue to try to get their people on the ground and see whether it's sufficient," she added.

But Nuland warned that if the Syrian government did not fulfill all promises to the Arab League, "more action and more pressure was going to be required," citing potential actions at the UN Security Council and increased sanctions.