Less than four weeks since the end of Israel’s building freeze in the West Bank, hundreds of units are under construction in dozens of settlements there, settler leaders and anti-settlement advocates said Thursday.

Foundations have been dug for 300 units and work is under way on a couple of hundred more, they report, many of the units in smaller settlements that would be most unlikely to remain as part of Israel in any future two-state deal with the Palestinians.

Hagit Ofran, who monitors settlement construction for Peace Now, a group that opposes it, said she was preparing a report showing that in at least 36 settlements, especially in smaller ones, intensive building was under way.

“They suspect another freeze is coming, and they are running to build,” she said in a telephone interview. “This is also about selling and money, not only ideology. There is less government building and much more private building in areas that received approval a long time ago and where there is demand.”

In the largest settlements, where government approval is required to break ground, building has resumed at a slower pace, she said.

Peace talks between Israel and the Palestinian Authority ended late last month when the 10-month settlement construction freeze ended. The Palestinians say they cannot negotiate while the land they seek as their future state is being covered in new Jewish housing.

The United States has been trying to persuade Israel to impose a second freeze to keep the talks going. Prime Minister Benjamin Netanyahu has said he is considering it.

Robert H. Serry, the United Nations special envoy for Middle East peace, issued a statement condemning the new West Bank building.

“Renewed settlement construction, which is illegal under international law, runs contrary to the international community’s repeated appeals to the parties to create conditions conducive to negotiations, and will only further undermine trust,” he said. “We continue to strongly support efforts to create conditions for the resumption of successful negotiations.”

The relative pace of the new construction is hard to measure because, in some cases, the building sites were ready before the 10-month freeze, and the activity at those sites resumed in the last few weeks.

Between 2006 and 2008, 3,000 units were built per year, according to Israel’s Central Bureau of Statistics. In the past year, 3,000 units were also built, grandfathered in before the freeze started.

Counting units with foundations — 300 so far — the rate is somewhat higher than in recent years. Ms. Ofran of Peace Now said that there clearly was pent-up demand because of the freeze and that it could account for some of the rate increase.

But she also said that construction patterns appeared to be shifting in light of political considerations. In the past, she said, ground was cleared and infrastructure, including sewage lines and electricity, were installed before foundations were dug. But since the freeze of last November labeled a foundation as proof of permanence, allowing the unit to be completed, she saw a new focus on digging foundations right away.

Assuming a second freeze following the pattern of the last one, units without foundations would be cleared away.

Settler leaders confirmed Ms. Ofran’s numbers and said they wished they had been able to build still more.

“Why should there be any place in Israel where we are barred from building?” asked Naftali Bennett, director of the Yesha Council, the settler group. He called the continuing building and settling of Jews in the West Bank a “necessary shield” to protect Israel.

The Associated Press did its own count of housing starts in the West Bank since the end of the freeze and found that 544 units were being built. It did not use foundations as a criterion for inclusion. The number was based on visits to 16 of the West Bank’s 120 settlements and reports from dozens of other settlements and interviews with mayors and construction workers.