A year after Israel's war in the Gaza Strip, an unprecedented calm has held around the Hamas-run enclave, but both sides are busily preparing for the inevitable next round, analysts say.

Since Israel's massive 22-day offensive to stop rocket fire from Gaza ended in reciprocal ceasefires on January 18, the borders of the territory have remained largely quiet despite violations by both sides.

"Not one soldier or Israeli citizen was killed in acts of terror in the winter of 2009, a phenomenon which we have not seen in the past decades," the head of Israeli military intelligence General Amos Yadlin was quoted as saying.

Each side has its own reasons for keeping the status quo, analysts say.

"Both Hamas and Israel are interested to maintain the current (situation). Israel wants a degree of political stability, and Hamas needs to rebuild its war capacity," said David Hartwell, a senior Middle East analyst at Jane's, a London-based information group specialising in defence issues.

But behind the quiet exterior, regional foes are busy preparing for the next conflict, which is certain to erupt sooner or later.

"Because both sides expect a conflict, eventually it happens," Hartwell said.

Israel has poured millions of dollars into developing defensive shields against the makeshift rockets often fired from Gaza as well as the more sophisticated weapons used by Lebanon's Hezbollah militia in its 2006 war with Israel, or the medium-range missiles in the arsenal of arch-foe Iran.

Although "there has been a steady improvement in security along our borders... our enemies have significantly improved their capabilities to fire precisely and for an extended time at the Israeli homefront," said Brigadier General Aviv Kochavi of the Israeli army's operations branch.

"Behind it all, to a large extent, is Iran," he said.

Iran supports both Hamas and Hezbollah, although there are disagreements over the extent of the aid. Israel says Iran gives them arms and training, while Tehran says it provides only moral support.

For Hamas, the lull is a time to restock arsenals in Gaza, which has been under a strict Israeli-Egyptian blockade since the Islamists seized power in June 2007, ousting forces loyal to Western-backed Palestinian president Mahmud Abbas.

The lion's share of Hamas's weapons are smuggled into the territory via tunnels on the border with Egypt and the group is notoriously secretive about the types of weapons it has.

But in September its political supremo Khaled Meshaal boasted that the group was procuring weapons by all means at its disposal.

"Your brothers in Palestine, despite the blockade and the closing of border passages ... we buy arms, we manage to produce arms and we smuggle arms," he said during a trip to Sudan.

Israel says that the smuggling has included more and more sophisticated weapons, including a rocket that is capable of reaching its densely populated commercial centre Tel Aviv.

Hamas has called the claim a "fabrication."

Hamas "is rebuilding its forces, recruiting more militants, and testing new equipment to be more efficient in the next military escalation against Israeli forces," a senior Israeli military commander said.

Hamas's rearming efforts may be severely hampered, however, by an underground barrier that Egypt is building on its border with Gaza, where most of the smuggling tunnels lie.

The steel barrier, which an Egyptian state-owned daily last week finally confirmed was under construction, will reportedly reach up to 30 metres (100 feet) into the ground and extend some 10 kilometres (six miles).